Journals >Chinese Journal of Lasers
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2012
Volume: 39 Issue 11
42 Article(s)
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Research Article
A Differential Absorption Lidar System for Tropospheric Ozone Monitoring
Fan Guangqiang, Liu Jianguo, Chen Zhenyi, Liu Wenqing, Lu Yihuai, Zhang Tianshu, and Dong Yunsheng
The differential absorption lidar is an advanced instrument for monitoring atmospheric ozone concentration profile. A new vehicle differential absorption lidar is developed. The lidar system emits four wavelengths ultraviolet laser based on a frequency quadrupled NdYAG laser and Raman shifting technique. A Cassegrain tThe differential absorption lidar is an advanced instrument for monitoring atmospheric ozone concentration profile. A new vehicle differential absorption lidar is developed. The lidar system emits four wavelengths ultraviolet laser based on a frequency quadrupled NdYAG laser and Raman shifting technique. A Cassegrain telescope is used and the grating spectrometer is used to separate the backscatter signals of the four emited wavelengths. The data is collected by photon counting and analog acquisition integration mode. The accuracy of measurement system is discussed and analyzed. The lidar system and ozonesonde under took experiments at the same time. Experimental results show that tropospheric ozone profiles derived from lidar and ozonesonde are in good agreement, suggesting that the vehicle differential absorption lidar system and ozone concentration analysis software are reliable..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1113001 (2012)
Holography and Information Processing
A Real-Time Target Detection Algorithm for Infrared Search and Track System Based on Region of Interest Extraction
Wang Weihua, Li Zhijun, He Yan, and Chen Zengping
With regard to the difficulties confronted in the aerial target detection of circumferential scan infrared search and track system, such as large image data quantity, low detection probability of weak target, high false detection rate and so on, a real-time target detection algorithm is proposed based on region of inteWith regard to the difficulties confronted in the aerial target detection of circumferential scan infrared search and track system, such as large image data quantity, low detection probability of weak target, high false detection rate and so on, a real-time target detection algorithm is proposed based on region of interest (ROI) extraction. It extracts the ROI of the suspected targets by quick real-time algorithm in the whole panorama image, based on the high frequency and movement characteristics of the target pixels. And then, focusing on the suspected target sliced images of ROI, it has further delicate detection and recognition to exclude those false jamming. The detection result of the test images shows, the algorithm has realized stable detection with low-rate false alarm for distant dim targets, and has been applied to the engineering sample of the panorama infrared search and tracking system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1109001 (2012)
Improvement of Least-Square Phase Unwrapping Algorithm Based on Lateral Shearing Interferometry
Qian Xiaofan, Li Bin, Li Xinghua, Lin Chao, Yuan Caojin, and Shi Ying
It is a tough question to obtain an unwrapping phase when the under-sampling happens. Although the least-square algorithm based on lateral shearing interferometry (LSBLS) has good anti-sub sampling ability, a satisfactory result can not be obtained when the under-sampling is serious. To solve this problem, a correspondIt is a tough question to obtain an unwrapping phase when the under-sampling happens. Although the least-square algorithm based on lateral shearing interferometry (LSBLS) has good anti-sub sampling ability, a satisfactory result can not be obtained when the under-sampling is serious. To solve this problem, a corresponding analysis is presented and the LSBLS algorithm is improved by introducing a second shearing. The validity of this improved algorithm is showed in one simulated result and one experimental result. It is promised, by the algorithm, the validity of unwraped phase, when the absolute value of discrete secondary derivative of wrapped phase is less than π..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1109002 (2012)
Laser Manufacturing
N2/Ar Aiding Laser In-Situ Synthesized TiN Particle Reinforced Titanium Matrix Composite Coating
Zhang Xiaowei, Liu Hongxi, Jiang Yehua, and Wang Chuanqi
By utilizing the high-temperature chemical reaction between Ti and AlN, TiN reinforced titanium matrix composite coating is in-situ synthesized on TC4 alloy substrate by laser cladding technique under nitrogen and argon atmosphere, respectively. The microstructure, micro-hardness and relative oxidation resistance of trBy utilizing the high-temperature chemical reaction between Ti and AlN, TiN reinforced titanium matrix composite coating is in-situ synthesized on TC4 alloy substrate by laser cladding technique under nitrogen and argon atmosphere, respectively. The microstructure, micro-hardness and relative oxidation resistance of treated samples are examined by X-ray diffraction, scanning electron microscopy, micro-hardness tester and air furnace. The results show that the microstructure and cross section micro-hardness distribution of laser cladding composite coating are more uniform under nitrogen atmosphere than those under argon atmosphere, and the in-situ combustion synthesis reaction is more fully. The composite coating is mainly composed of TiN and Ti3Al phase under nitrogen atmosphere, while it is mainly composed of TiN and α-Ti phase under argon atmosphere. The average micro-hardness of laser in-situ synthesized composite coating changes gradually and increases by 40.7% under nitrogen atmosphere; however, it changes sharply under argon atmosphere. The relative oxidation resistance values of laser cladding composite coating at 600 ℃ and 800 ℃ under nitrogen atmosphere are 6.83 and 1.94 times of those of the TC4 alloy substrate, and increase by 17.96% and 19.75% than those under argon atmosphere, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1103001 (2012)
Temperature Flied Simulation on Aluminium Alloy Irradiated by Long Pulsed Laser and Continuous Wave Laser
Xiao Jing, He Hengxiang, Xia Huijun, and Jia Jing
Finite element analysis software ANSYS is used to simulate the temperature distribution of 2A12 irradiated by continuous wave (CW) laser and long pulsed laser. The effect of different intervals of time between the two beams on the maximum temperature of the center and the size of molten pool and the effect of differentFinite element analysis software ANSYS is used to simulate the temperature distribution of 2A12 irradiated by continuous wave (CW) laser and long pulsed laser. The effect of different intervals of time between the two beams on the maximum temperature of the center and the size of molten pool and the effect of different combinations of the two lasers′ radiuses are investigated. The results show that the maximum temperature of the center increases by increasing the interval of time. The temperature rise induced by long pulsed laser increases when the interval of time is larger than one specific value. The maximum temperature of the center and the size of molten pool are mainly decided by the long pulsed laser which has a relatively higher peak power, the continuous wave laser used to preheat the material can significantly increase the size of molten pool when its power density is at 105 W/cm2 level..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1103002 (2012)
Laser Physics
Laser Diode with Long External Cavity of Volume Bragg Grating
Li Zhiyong, Tan Rongqing, Huang Wei, Xu Cheng, and Li Lin
In order to achieve beam combination of volume Bragg grating diode lasers (VBLs) in the external cavity, characteristics of VBL with long cavity length is studied. A plane convex cylindrical lens with focal length of 25 mm is used to collimate the single emitter laser diode (LD) in slow axis direction. Meanwhile, volumIn order to achieve beam combination of volume Bragg grating diode lasers (VBLs) in the external cavity, characteristics of VBL with long cavity length is studied. A plane convex cylindrical lens with focal length of 25 mm is used to collimate the single emitter laser diode (LD) in slow axis direction. Meanwhile, volume Bragg grating (VBG) is positioned off-axis in fast axis of the LD. External cavity length of about 240 mm is established, and the linewidth is narrowed from 1.8 nm of free-running diode to 0.14 nm. In the experiment, characteristics of the VBL are unchanged for different polarizations of laser. By adjusting the VBG′s temperature, a tunable range from 779.18 nm to 779.75 nm of the VBL with long cavity length is realized while the linewidth remains the same..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1102006 (2012)
Whispering Gallery Mode Fiber Laser Based on PDMS Substrate
Zhang Yuanxian, Zhang Xiaoxiao, Liu Chun, and Pu Xiaoyun
A whispering-gallery-mode (WGM) fiber laser integrated on a polydimethylsiloxane (PDMS) chip is presented which consists of a multimode quartz optical fiber, plastic wedge optical fiber, lasing dye solution, a glass and a PDMS substrate. A multimode quartz unclad optical fiber with a diameter of 279 μm and a plastic weA whispering-gallery-mode (WGM) fiber laser integrated on a polydimethylsiloxane (PDMS) chip is presented which consists of a multimode quartz optical fiber, plastic wedge optical fiber, lasing dye solution, a glass and a PDMS substrate. A multimode quartz unclad optical fiber with a diameter of 279 μm and a plastic wedge optical fiber with a diameter of 200 μm are coupled and fixed on a glass substrate, and the length and width of the glass substrate are 2 cm and 1 cm, respectively. By pouring liquid PDMS on the glass substrate and oven dry, a flexible PDMS substrate (thickness is about 400 μm) is shaped. Then a fiber channel (length is 0.4 cm, both width and height are 400 μm) is carved in the contact position between PDMS and the coupled optical fiber. After injecting ethanol solutions of rhodamine 6G into the channel and packaging by a cover glass, a WGM laser chip integrated on a PDMS substrate is fabricated. Pumped by evanescent wave along the quartz optical fiber axis, low threshold energy of 8.5 μJ and directional WGM lasing emission has been successfully achieved on a PDMS chip..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1102001 (2012)
CW Mode-Locked Yb:NaY(WO4)2 Femtosecond Laser with a Semiconductor Saturable-Absorber Mirror
Zhang Haikun, Cui Xuelong, Xu Jinlong, Yang Ying, He Jingliang, and Tu Chaoyang
Yb:NaY(WO4)2 crystal is grown by the Czochralski method and a laser diode-pumped mode-locked Yb:NaY(WO4)2 femtosecond laser with a semiconductor saturable-absorber mirror (SESAM) is experimentally demonstrated. The average output power of 164 mW is obtained with the incident pump power of 8.6 W. The pulse duration is mYb:NaY(WO4)2 crystal is grown by the Czochralski method and a laser diode-pumped mode-locked Yb:NaY(WO4)2 femtosecond laser with a semiconductor saturable-absorber mirror (SESAM) is experimentally demonstrated. The average output power of 164 mW is obtained with the incident pump power of 8.6 W. The pulse duration is measured to be 246 fs with a repetition rate of 35 MHz at the central wavelength of 1035 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1102002 (2012)
Fast Close-Loop Phase Control to Output Transform-Limited Femtosecond Laser Pulses
Qian Cheng, Wang Sijia, Gu Chenglin, Zhang Limeng, Liu Bowen, Pang Dongqing, Hu Minglie, Chai Lu, and Wang Qingyue
A close-loop chirp compensation system which consists of a simplified frequency-resolved optical gating (FROG) device and liquid crystal spatial light modulator (LC-SLM) is demonstrated. Femtosecond laser pusles are measured by using simplified frequency-resolved optical grating. The phase feedback signals derived fromA close-loop chirp compensation system which consists of a simplified frequency-resolved optical gating (FROG) device and liquid crystal spatial light modulator (LC-SLM) is demonstrated. Femtosecond laser pusles are measured by using simplified frequency-resolved optical grating. The phase feedback signals derived from the simplified FROG control the LC-SLM to compensate the chirp of pulses. As a result, 74-fs transform-limited pulses are obtained from nonlinear fiber femtosecond laser amplifier..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1102003 (2012)
Thermal Effects Analysis of Nd∶CNGG 935 nm Laser Pumped by 885 nm and 808 nm Diode Lasers
Shi Yuxian, Lu Tielin, Feng Baohua, Zhang Huaijin, Yu Haohai, and Wang Jiyang
The thermal lensing effects of 808 nm and 885 nm LD end-pumped NdCNGG 935 nm laser are investigated by experimental and theoretical methods. The thermal focal length of the laser pumped by 885 nm is about 6.8 times of the one pumped by 808 nm when the absorbed power reaches to 10 W. Meanwhile, the temperature gradient The thermal lensing effects of 808 nm and 885 nm LD end-pumped NdCNGG 935 nm laser are investigated by experimental and theoretical methods. The thermal focal length of the laser pumped by 885 nm is about 6.8 times of the one pumped by 808 nm when the absorbed power reaches to 10 W. Meanwhile, the temperature gradient in crystal is smaller under 885 nm pumping. At the pump waist position, the maximal values of the crystal temperature under 885 nm and 808 nm pumping are 287.76 K and 310.05 K, respectively, in experiment. At the pump face, the maximal values of the crystal temperature under 885 nm and 808 nm pumping are 285.78 K and 317.18 K. Compared with the 808 nm pumping scheme, the slope efficiency increases by 43% (from 4.6% to 6.6%) with an 8% reduction (from 3.31 W to 3.05 W) in the oscillation threshold under 885 nm direct pumping scheme..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1102004 (2012)
Tunable Multiwavelength Brillouin/Erbium Fiber Laser with Double-Brillouin-Shift Spacing
Zhang Cheng, Miao Changyun, Zhao Junfa, and Tong Zhengrong
A tunable multiwavelength Brillouin/erbium fiber laser with double-Brillouin-shift spacing is experimentally demonstrated. The compound ring cavity configuration formed by a 3 dB coupler confines the odd-order Stokes signals to circulate in a cavity and provides the initial Brillouin pump and even-order Stokes signals A tunable multiwavelength Brillouin/erbium fiber laser with double-Brillouin-shift spacing is experimentally demonstrated. The compound ring cavity configuration formed by a 3 dB coupler confines the odd-order Stokes signals to circulate in a cavity and provides the initial Brillouin pump and even-order Stokes signals to be coupled out. Then multiwavelength outputs with double-Brillouin-shift spacing are achieved. The output characteristics of the fiber laser are analyzed under different Brillouin pump powers and 980 nm pump powers. At the Brillouin pump power of 10 dBm and the 980 nm pump power of 110 mW, 6 output channels with 0.176 nm channel spacing from 1555 nm to 1565 nm are achieved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1102005 (2012)
1.3 μm Picosecond Regenerative Amplifier with High Pulse Energy
Wang Lulu, Niu Gang, Shi Zhaohui, Yan Ying, Ma Yunfeng, Huang Yutao, Fan Zhongwei, Mikhail Grishin, Donatas Joksas, and Zenonas Kuprionis
A laser diode pumped 1.3 μm high energy picosecond regenerative amplifier is reported. The passively mode-locked oscillator as a seed source provides repetition rate of 65 MHz and power of 140 mW. An effective regenerative amplifier is designed. The regenerative amplifier is operated at 1 kHz and its pulse duration is A laser diode pumped 1.3 μm high energy picosecond regenerative amplifier is reported. The passively mode-locked oscillator as a seed source provides repetition rate of 65 MHz and power of 140 mW. An effective regenerative amplifier is designed. The regenerative amplifier is operated at 1 kHz and its pulse duration is shorter than 20 ps. Its output pulse energy is 1 mJ. Its pulse stability root mean square is less than 0.3%. The beam quality factor M2 is less than or equal to 1.1 after second harmonic generation to 671 nm, which shows its good beam profile..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1102007 (2012)
Materials and Thin Films
Highly Nonlinear All-Solid Photonic Crystal Fibers with Low Dispersion Slope
Xu Huizhen, and Zhou Changjie
Fluorine-doped (F-doped) trench-assisted structure is proposed to improve the nonlinearity of photonic crystal fibers (PCFs). Through controlling only two parameters, three all-solid highly nonlinear PCFs with low dispersion slope and low confinement loss are designed. They exhibit all normal dispersion, two zero dispeFluorine-doped (F-doped) trench-assisted structure is proposed to improve the nonlinearity of photonic crystal fibers (PCFs). Through controlling only two parameters, three all-solid highly nonlinear PCFs with low dispersion slope and low confinement loss are designed. They exhibit all normal dispersion, two zero dispersion wavelengths (ZDWs) and one ZDW just at 1.55 μm, respectively. The dispersion slope of one ZDW just at 1.55 μm is 5.12×10-4 ps/(km·nm2), which is two order of magnitude lower than that of conventional highly nonlinear fibers. A nonlinear coefficient of 31.5 W-1·km-1 and loss low of 9.62×10-5 dB/km at 1.55 μm are achieved for this PCF..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1106001 (2012)
Fluorescence Properties of Al3+/Eu2+ Co-Doped High Silica Glass
Gong Fanhan, Qian Qi, Yang Zhongmin, Zhang Qinyuan, Liu Yanchun, Zhang Qi, Hou Laiguang, and Song Wuyuan
Al3+/Eu2+ co-doped high silica glass is obtained by sintering porous glass impregnated in Al3+ and Eu2+ ion-containing solutions. Effects of different Al3+ concentrations on the fluorescence intensity and the emission peak of Eu2+ ions in high silica glass under ultraviolet (UV) excitation are investigated. The resultsAl3+/Eu2+ co-doped high silica glass is obtained by sintering porous glass impregnated in Al3+ and Eu2+ ion-containing solutions. Effects of different Al3+ concentrations on the fluorescence intensity and the emission peak of Eu2+ ions in high silica glass under ultraviolet (UV) excitation are investigated. The results show that, with the properly increased concentrations of Al3+, a remarkable increase in the flourescence intensity of Eu2+ ions centered at 450 nm under UV excitation can be observed because of both the action of Al3+ ions dispersing Eu2+ ions in the high silica glass matrix and the lower phonon energy of Al2O3. Meanwhile, since Al3+ codopant decreases the splitting extent of 5d energy band of Eu2+ ion in high silica glass, an obvious blue shift of the emission peak of Eu2+ ions can be observed with increasing Al3+ content..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1106002 (2012)
Experimental Study of Four-Channel Frequency Division Multiplexed Fluorescence Confocal Microscopy
Tang Pingyu, Zheng Jihong, Sun Guoqiang, Zhang Menghua, Guo Caihong, and Zhuang Songlin
We report an experimental study of four-channel frequency division multiplexed fluorescence confocal microscopy (FDMFCM) detection system modulated by holographic polymer dispersed liquid crystal (H-PDLC) Bragg grating array chopper. In the system, fluorescence signal is excited by the exciting light focused on the bioWe report an experimental study of four-channel frequency division multiplexed fluorescence confocal microscopy (FDMFCM) detection system modulated by holographic polymer dispersed liquid crystal (H-PDLC) Bragg grating array chopper. In the system, fluorescence signal is excited by the exciting light focused on the biological sample, and then is detected. Fourier transform, filtration and demodulation are then carried out to restore the fluorescence signal with a curve of four-channel fluorescence signal intensity versus time. The four-channel FDMFCM system is experimentally set up with 405 nm laser as the excitation light, and the image and intensity information of the fluorescence signal, which are excited from the mouse neural hippocampus cell sample, are successfully detected..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1106003 (2012)
Fabrication of 8-Channel Micro Integrated Filter in 2.0～2.4 μm by Combine Masks and Plating
Luo Haihan, Li Yaopeng, Cai Qingyuan, and Liu Dingquan
Using the method to combine masks and plating the spacer layer of the Fabry-Perot filter, germanium and silicon oxide are selected as the high and low index coating materials, 8-channel integrated filter is designed and fabricated with an effective light-transmitting width of 450 μm separated by a block of 30 μm for eaUsing the method to combine masks and plating the spacer layer of the Fabry-Perot filter, germanium and silicon oxide are selected as the high and low index coating materials, 8-channel integrated filter is designed and fabricated with an effective light-transmitting width of 450 μm separated by a block of 30 μm for each channel in the spectral regions of 2.0～2.4 μm. For each channel, the maximum transmittance is greater than 65%, the full width at half maximum (FWHM) is 8～13 nm, as well as, the relative bandwidth is between 0.33%～0.65%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1107001 (2012)
Measurement and Metrology
Error Analysis of the Moving Mirror Tilting in Michelson Wind Imaging Interferometer with Big Optical Path Difference, Wide Field, Adromatism and Thermal Compensation
Zhu Baohui, Zhang Chunmin, Lu Huidong, and Zeng Wenfeng
On fixed optical path difference, interference intensity of four steps in an interval of quarter of wavelength is achieved by moving mirror step of λ/4 for Michelson wind imaging interferometer (MWII) with large optical path difference, wide field, chromatic compensation and thermal compensation. In this way, the inforOn fixed optical path difference, interference intensity of four steps in an interval of quarter of wavelength is achieved by moving mirror step of λ/4 for Michelson wind imaging interferometer (MWII) with large optical path difference, wide field, chromatic compensation and thermal compensation. In this way, the information of velocity, air pressure and temperature for aerosphere can be achieved. In this course, the error of fixed optical path difference, step error and tilting of the moving mirror will affect the results. To better meet the actual application and engineering for MWII, the tolerance of the error for tilting of the moving mirror is discussed in the range of allowance precision, the method of the error is derived, and the curves of the relationship between the temperature, velocity and the tilting of the moving mirror are simulated by computer. This work has a great meaning on the theory research, capability improvement, engineering of MWII and will be useful for the application of Michelson interferometer on the passive measurement of the wind field in the upper atmosphere..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108001 (2012)
Digital Moiré Technique for Thin Film Thickness Measurement
Su Junhong, and Liu Yichen
The core of the modern interferometry is to obtain the necessary surface shape and parameters by processing the interferogram using the reasonable algorithm. The method of the common phase shifting interferometry is to obtain the wave surface by digitalizing the multiple interferogram which is gained by the ordered traThe core of the modern interferometry is to obtain the necessary surface shape and parameters by processing the interferogram using the reasonable algorithm. The method of the common phase shifting interferometry is to obtain the wave surface by digitalizing the multiple interferogram which is gained by the ordered translation motion of the phase shifter, which will introduce a calculation error produced by linear and nonlinear error of phase shifter. Therefore, the phase shifter must be calibrated first. The digital Moiré technique is used, which is to separately overlay a static interferogram with four surfaces of intensity distribution of the sinusoidal grating with different light distribution, achieving the effect of dynamic test based on the phase shifting interferometry, then to obtain the phase distribution based on the principle of the phase shifting interferometry, and thus to realize the measurement of thin film thickness. The initial phase of the sinusoidal grating is generated by the computer, so this phase shift has no error on phase shift, which makes the accuracy of measurement improved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108002 (2012)
Camera Pose Estimation Based on Virtual Control Points
Chen Peng, Hu Guangda, and Liu Xiaojun
Camera pose estimation, including the estimation of rotation matrix and translation vector, has extensive applications in machine vision area. In this paper, an iterative algorithm based on virtual control points is proposed. The basic idea is to acquire the camera pose estimation in a short time by using fewer virtualCamera pose estimation, including the estimation of rotation matrix and translation vector, has extensive applications in machine vision area. In this paper, an iterative algorithm based on virtual control points is proposed. The basic idea is to acquire the camera pose estimation in a short time by using fewer virtual control points, and to realize a detailed adjustment by using the famous orthogonal iterative algorithm, so that the accuracy and the stability of the whole algorithm can be improved. Experimental results show that the performance of the proposed algorithm is better than most popular iterative algorithms for camera pose estimation, and it has a strong ability of resisting both noise disturbing and error registration of control points. Furthermore, it can be applied in real measurement environment. Therefore, the proposed algorithm is an effective algorithm for camera pose estimation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108003 (2012)
Temperature Measurement of CO2 by Use of a Distributed-Feedback Diode Laser Sensor Near 2.0 μm
Chen Jiuying, Liu Jianguo, He Yabo, Xu Zhenyu, Li Han, Yao Lu, Yuan Song, Ruan Jun, He Junfeng, and Kan Ruifeng
Temperature measurement is realized by scanning two absorption lines of CO2 using distributed-feedback diode laser near 2.0 μm. The fundamental of temperature measurement by tunable diode laser absorption spectroscopy (TDLAS) is introduced, and multi-line nonlinear fitting method is proposed. The experiment is carried Temperature measurement is realized by scanning two absorption lines of CO2 using distributed-feedback diode laser near 2.0 μm. The fundamental of temperature measurement by tunable diode laser absorption spectroscopy (TDLAS) is introduced, and multi-line nonlinear fitting method is proposed. The experiment is carried out in a heated static quartz cell at normal pressure. Within the temperature range from 900 K to 1200 K, the difference between TDLAS and S-thermocouple is less than 8%. Relative error between measured line-strength at 5007.7874 cm-1 and the theoretical value is less than 14%. The result analysis can be useful for the further research on concentration and temperature measurement by a single diode laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108004 (2012)
Measurement System for Laser Divergence Angle Based on LabView
Wang Qianqian, Liu Jia, Peng Zhong, and Liu Li
In order to measure the laser beam-divergence on-line during the laser manufacture, a divergence angle measurement system for pulse laser is established. It is based on the focus method. The laser beam widths are measured by using variable aperture method. In order to improve its automation, a test software is built baIn order to measure the laser beam-divergence on-line during the laser manufacture, a divergence angle measurement system for pulse laser is established. It is based on the focus method. The laser beam widths are measured by using variable aperture method. In order to improve its automation, a test software is built based on LabView software. It will realize automatic measurement with different diameter apertures, record the relevant energy, compute the dirergence angle of laser, save and type the results. Experimental results show that the error of this measurement system is below 0.05 mrad which can fulfill the requirements of divergence angle test..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108005 (2012)
Cloud Recognition from Infrared Remote Sensing Images under City Background
Li Zhijun, Wang Weihua, Niu Zhaodong, Liu Songlin, and Chen Zengping
Aiming at the problem of infrared remote sensing cloud detection under complex surface features background, a novel cloud detection algorithm based on image feature extraction, regional voting and threshold segmentation is proposed. Denoising and normalized stretching are performed on image. The multi-features are extrAiming at the problem of infrared remote sensing cloud detection under complex surface features background, a novel cloud detection algorithm based on image feature extraction, regional voting and threshold segmentation is proposed. Denoising and normalized stretching are performed on image. The multi-features are extracted and cloud discrimination is executed in sub-region using the extracted feature vectors. The precise cloud regions are obtained through threshold segmentation based on discrimination results and fractal characteristics. Test results show that the accuracy of image recognition is above 91%. The applicability and effectiveness of the algorithm is verified by large quantities of measured data and it provides effective technical support for the information processing of infrared remote sensing image..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108006 (2012)
Design and Stability Analysis of Interferometry Frame
Zhou Feng, Wang Hui, and Wang Liping
Repeatability of interferometry depends on the stability of metrology frame to a certain extent, according to the requirements of stability, structure of the frame is designed. Aiming at the stability problem of high precision metrology frame caused by random vibration, the finite element model of a metrology frame is Repeatability of interferometry depends on the stability of metrology frame to a certain extent, according to the requirements of stability, structure of the frame is designed. Aiming at the stability problem of high precision metrology frame caused by random vibration, the finite element model of a metrology frame is established, the power spectral density (PSD) measured on the fixed platform is used as the excitation, and then the random vibration response of the frame is analyzed with the PSD module of ANSYS. The analyzed result of stability is 0.5144 nm, and the experimental value is 0.653 nm, they are in good agreement, and the structure of frame and the actual vibration condition meet the stability requirements of metrology frame..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108007 (2012)
Development of Mirror Mount for Ultra-High Reproducibility Metrology
Wang Hui, Yu Jie, Zhou Feng, and Wang Liping
In order to improve the reproducibility in mirror metrology, a mirror mount used in high repeatability interferometer is developed, and simulations and testing are undertaken to evaluate the device. The deformation of the mirror due to disturbance in the mount is analyzed with ANSYS and the reproducibility of differentIn order to improve the reproducibility in mirror metrology, a mirror mount used in high repeatability interferometer is developed, and simulations and testing are undertaken to evaluate the device. The deformation of the mirror due to disturbance in the mount is analyzed with ANSYS and the reproducibility of different metrology mount is calculated. The calculation results indicate that root mean square (RMS) of the reproducibility that the mount can be achieved is better than 30 pm. The structure of the device is finally confirmed, and reproducibility testing is carried out on high repeatability interferometer, the testing result indicates that RMS of the reproducibility caused by the mount devise is better than 70 pm, which meet the 0.1-nm RMS requirement of the error budget..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108008 (2012)
Frequency Selection Rule based on Robust Chinese Remainder Theorem and Its Application in Phase Unwrapping
Zhang Xu, Zhu Limin, Tu Dawei, and Fan Lingling
Phase unwrapping is an essential problem in phase measuring profilometry. In this paper, phase unwrapping is modeled as a congruence problem. Based on robust Chinese remainder theorem, the frequency selection rule is proved by analyzing the uncertainty of wrapped phase because of the intensity noise. Then, this rule isPhase unwrapping is an essential problem in phase measuring profilometry. In this paper, phase unwrapping is modeled as a congruence problem. Based on robust Chinese remainder theorem, the frequency selection rule is proved by analyzing the uncertainty of wrapped phase because of the intensity noise. Then, this rule is adopted to design the frequency unwrapping algorithm and the parameters are determined with high confidence probability. After that, the closed-form algorithm of robust Chinese remainder theorem is employed to determine the correspondence. Finally, the quantitative comparisons are implemented in our developed structured light measurement system. The experimental results show that the frequency selection rule is valid, and robust Chinese remainder theorem is less sensitive to the phase noise than the traditional Chinese remainder theorem. If the frequency selection rule is satisfied, the accuracy of the unwrapped phase can achieve nearly 100%, otherwise, the performance is deteriorated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108009 (2012)
Finite Element Modeling of Subsurface Recognition for Pulsed Thermography
Tao Ning, Zeng Zhi, Feng Lichun, Kong Dejuan, and Zhang Cunlin
ANSYS is used to simulate the detection process of pulsed thermography, and it simulates one steel sample with two depths and four kinds of defects under the excitation of planar heat flow. The temperature evolution and distribution of the detected surface of steel sample are calculated, the temperature decay curves coANSYS is used to simulate the detection process of pulsed thermography, and it simulates one steel sample with two depths and four kinds of defects under the excitation of planar heat flow. The temperature evolution and distribution of the detected surface of steel sample are calculated, the temperature decay curves corresponding to the defects areas are extracted to calculate the reflective coefficients of the interface between steel and defects, and the calculation results are compared with the experimental results of pulsed thermography. The possibility of identifying the subsurface defect characteristics by finite element (FE) modeling is studied, and it can be used as reference for pulsed thermography to be used for quantitatively detection..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108010 (2012)
Wavefront Reconstruction with Orthonormal Polynomials in a Square Area
Li Mengyang, Li Dahai, Wang Qionghua, Zhao Jiwen, Zhang Chen, Chen Yingfeng, and Zhang Chong
An orthonormal square Zernike basis set is generated from circular Zernike polynomial apodized square mask by use of the linearly independent set Gram-Schmidt orthogonalization technique. Based on the concepts of inner product, Euclidean space and norm in the linear algebra, a standard Zernike polynomial set is made orAn orthonormal square Zernike basis set is generated from circular Zernike polynomial apodized square mask by use of the linearly independent set Gram-Schmidt orthogonalization technique. Based on the concepts of inner product, Euclidean space and norm in the linear algebra, a standard Zernike polynomial set is made orthogonal and a new orthonormal basis of polynomials named Z-square polynomial is established. Wavefront data in square aperture can be fitted with our new orthonormal set. It can not only fit the wavefront data with Z-square basis set itself, but also can be linearly composed of standard Zernike basis set by linear reverse transform and endows the decomposed wavefront modes with a correspondent aberration meaning. The experimental results show that the Z-square polynomial set can fit the wavefront aberration data in lens design efficiently and can also fit the practical wavefront phase data of Hartmann-Shack wavefront sensor testing, it provides a method of wavefront data analysis..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108011 (2012)
Application of SLAM in Vehicle-Borne Mobile Mapping System
Hu Shaoxing, Chen Chunpeng, and Zhang Aiwu
To solve the GPS denies or no GPS positioning problem of the vehicle-borne mobile mapping system (VBMMS), a fast simultaneous localization and mapping (SLAM) method using the horizontal 2D laser scanner and the odometer is proposed. Through position error analysis of VBMMS, the scientific prediction and re-prediction pTo solve the GPS denies or no GPS positioning problem of the vehicle-borne mobile mapping system (VBMMS), a fast simultaneous localization and mapping (SLAM) method using the horizontal 2D laser scanner and the odometer is proposed. Through position error analysis of VBMMS, the scientific prediction and re-prediction parameters are set. An improved extended Kalman filter (EKF) based on wide-interval prediction and re-predition are presented to speed up. The experiments done in the closed corridor show the method mentioned above are reliable..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108012 (2012)
Multi-Point Calibration Method Based on Stokes Ellipsometry System
Wang Yonghui, Zheng Chunlong, and Zhao Zhentang
Stokes ellipsometer can quickly measure polarization state of light beam. Accurate measurement of instrument matrix is one of the most important technology in stokes ellipsometer. In order to improve measurement accuracy of the instrument matrix, a method of multi-point calibration for stokes ellipsometry system is proStokes ellipsometer can quickly measure polarization state of light beam. Accurate measurement of instrument matrix is one of the most important technology in stokes ellipsometer. In order to improve measurement accuracy of the instrument matrix, a method of multi-point calibration for stokes ellipsometry system is proposed and is proved in theory. Six-point calibration method based on multi-point calibration method is used on the system, which is verified by experiment. Results show that using multi-point calibration method calibration of the system is entirely feasible. It provides a new approach for calibration of Stokes ellipsometer, and six-point calibration method is more accurate than standard of four-point and E-P calibration method in acquiring matrix of the instrument. In measurement accuracy, the total root-mean-square (RMS) deviation of Stokes parameters is 3.15%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108013 (2012)
Novel Calibration Method for Axes in Line Structured Light Vision Measurement System
Chen Xinyu, Ma Zi, Chen Tianfei, and Li Peng
In order to simplify calibration procedures of translation and rotation axes, a flexible calibration method based on one-dimensional plane target is proposed. Plane target is placed on platform, then the platform is translated and rotated, respectively. The centers of every concentric circle at each location are extracIn order to simplify calibration procedures of translation and rotation axes, a flexible calibration method based on one-dimensional plane target is proposed. Plane target is placed on platform, then the platform is translated and rotated, respectively. The centers of every concentric circle at each location are extracted. The spatial location of system axes are determined using principles of vanishing points and perspective-three-point (P3P). Experimental results indicate that this calibration method has high accuracy; its average absolute measuring accuracy is 0.0411 mm, and its root mean square (RMS) error is 0.0625 mm. This calibration method requires only three collinear points to complete high-precision calibration of translation and rotation axes, which therefore can reduce calibration cost. It concludes that the calculation is flexible and suitable for field calibration..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108014 (2012)
Measurement of Parallelism Between Rotating Axis and Guideway of a Machine Tool Based on Approximation Hole Center Positioning Method
Liu Xinbo, Wang Zhong, Su Ye, Liu Hongguang, and Zhu Jigui
For measuring the parallelism between the Z guide and the rotating axis of spindle on the machine tool, a new detection method which combines a machine tool probe based on laser displacement sensor with the approximation hole center positioning method is proposed. On the rule of keeping the rotating axis invariant, theFor measuring the parallelism between the Z guide and the rotating axis of spindle on the machine tool, a new detection method which combines a machine tool probe based on laser displacement sensor with the approximation hole center positioning method is proposed. On the rule of keeping the rotating axis invariant, the same center of a ring gauge which lies on different points of the rotating axis is located twice and the obtained coordinate values can be used to calculate the parallelism. The detection method can eliminate some of the drawbacks involved in the measurement methods with the physical mandrel, meanwhile, they can achieve measurement as the spindle is rotating in high speed. The experimental results show that this method can complete parallelism measurement of the guide and the rotating axis of spindle, so it is expected to be a new means for the calibration of machine tools..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108015 (2012)
Measurement of Geometric Error of Rotary Stage System Based on Laser Tracker
Zhang Zhenjiu, and Hu Hong
Rotary stage system is a fundamental part of multi-axis machine tools. Therefore, measuring geometric error of rotary stage system is significantly important for geometric error calibration of multi-axis machine tools. A method for measuring geometric error of rotary stage system based on laser tracker is proposed. HomRotary stage system is a fundamental part of multi-axis machine tools. Therefore, measuring geometric error of rotary stage system is significantly important for geometric error calibration of multi-axis machine tools. A method for measuring geometric error of rotary stage system based on laser tracker is proposed. Homogeneous transformation is applied to establish the mathematical model of geometric error of the rotary stage system which can explicitly describe the relationship between geometric errors and volumetric errors. The coordinates of three noncollinear points on the stage are detected by laser tracker and the volumetric errors of each point can be obtained too. The mathematical model of geometric error is performed inversely to achieve a system of equations which can be solved to obtain the six geometric errors of rotary stage system. This method is used to measure the geometric errors of a rotary stage, and the effectiveness of this method is validated by a comparison experiment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1108016 (2012)
Optical Communication
A MISO-OFDM Visible Light Communication System using LED Based on Subcarrier Multiplexing
Li Rongling, Tang Chanjuan, Wang Yuanquan, Wang Yiguang, Shao Yufeng, and Chi Nan
A novel configuration of 2×1 and 3×1 multiple-inputs single-output (MISO) multiple-inputs sigle output visble light communication (OFDM-VLC) system is reported experimentally. The error vector magnitude (EVM) values varying with the input voltage of 2×1 and 3×1 systems is measured, and the best rangA novel configuration of 2×1 and 3×1 multiple-inputs single-output (MISO) multiple-inputs sigle output visble light communication (OFDM-VLC) system is reported experimentally. The error vector magnitude (EVM) values varying with the input voltage of 2×1 and 3×1 systems is measured, and the best ranges of bias voltage is found, respectively. By setting the input voltage in the respective best range, the EVM values of 2×1 system, the EVM values and bit error rate (BER) of 3×1 system varying with transmission distance are presented. Without equalization, the transmission distance of the two systems can both be as long as 140 cm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1105001 (2012)
Generation of a Hollow Laser Beam by a Liquid-Core Optical Fiber
Hu Xiaobo, Liu Shengnan, Gao Wei, Sun Di, Zhang Hongying, and Zhang Liuyang
A method of producing a hollow laser beam (HLB) by directing the laser beam at a certain angle into a liquid core optical fiber (LCOF) is presented. The dependences of dark spot size DSS and beam width of the HLB on the propagation distance, and the length and core diameter of the LCOF are theoretically analyzed by modA method of producing a hollow laser beam (HLB) by directing the laser beam at a certain angle into a liquid core optical fiber (LCOF) is presented. The dependences of dark spot size DSS and beam width of the HLB on the propagation distance, and the length and core diameter of the LCOF are theoretically analyzed by modeling the generation system using Zemax. Using CS2 as core-liquid material, a part of theoretical result is experimentally demonstrated with 630 nm semiconductor laser. The results show that HLBs with adjustable DSS are obtained by changing the incident angle of the laser beam. DSS and beam width of the HLB are independent of the LCOF length, while related to its core diameter. This method has advantages of convenient operation, low cost and wide adjustable range of DSS. It can satisfy the needs of different applications..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1105002 (2012)
Theoretical Investigation of Photonic Crystal Fiber with Highly Nonlinear and Birefringent
Li Deyue, Zhou Guiyao, Xia Changming, Liu Jiantao, Yuan Jinhui, and Hou Lantian
According to the full-vector finite element method, a new highly nonlinear and birefringence photonic crystal fiber (PCF) with zero-dispersion at wavelength of 1550 nm is designed. The effective refractive index, effective mode area, birefringence, nonlinear coefficient and dispersion characteristics of the PCF are anaAccording to the full-vector finite element method, a new highly nonlinear and birefringence photonic crystal fiber (PCF) with zero-dispersion at wavelength of 1550 nm is designed. The effective refractive index, effective mode area, birefringence, nonlinear coefficient and dispersion characteristics of the PCF are analyzed. Simulation results show that birefringence of the PCF is 4.049×10-3, and nonlinear coefficient reaches 28.4 km-1·W-1 at wavelength of 1550 nm, which are obtained under the condition of cladding air hole pitch size of 1.6 μm, large air hole diameter of 1.4 μm and small air hole diameter of 0.74 μm and 0.76 μm respectively. The PCF has very broad prospect of application in 1550 nm communication band..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1105003 (2012)
Damage Monitoring of the Double-Notched Carbon Fiber Reinforced Polymers with Surface Bonded Chirped Fiber Bragg Grating Sensor
[in Chinese]
Chirped fiber Bragg grating (CFBG) sensors are sensitive to a non-uniform strain distribution along their longitudinal directions, and this effect is manifested in the power spectrum of the reflected light from the gage section. This paper describes a novel technique to monitor the damage of double-notched carbon fiberChirped fiber Bragg grating (CFBG) sensors are sensitive to a non-uniform strain distribution along their longitudinal directions, and this effect is manifested in the power spectrum of the reflected light from the gage section. This paper describes a novel technique to monitor the damage of double-notched carbon fiber reinforced polymers (CFRP) lamination using the surface bonded CFBG sensor. The experimental results show that the reflection spectra of the CFBG sensor change distinctively within certain wavelength when the static strains of CFRP reach to 4500 με and 8500 με, which coincides with the strain change point of 8000 με in stress-strain relationship curve of CFRP laminates. The sudden change points of the reflected spectra have an one-to-one correspondence with the location of CFBG. So the proposed approach is useful for predicting the damage states and location of the notch in composite laminates..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1105004 (2012)
A Novel Asymmetric Interleaver with Arbitrary Bandwidth Ratio Based on Planar Optical Waveguide
Li Jinxing, Chen Kaixin, and Zheng Yanlin
In order to improve transmission efficiency of optical-fiber communication system for hybrid 10 Gbit/s and 40 Gbit/s system, a novel device configuration for realizing an asymmetrical optical interleaver based on planar optical waveguide is proposed, which is a clever combination of optical micro-ring and Mach-Zehnder In order to improve transmission efficiency of optical-fiber communication system for hybrid 10 Gbit/s and 40 Gbit/s system, a novel device configuration for realizing an asymmetrical optical interleaver based on planar optical waveguide is proposed, which is a clever combination of optical micro-ring and Mach-Zehnder interferometers. Theoretical results show that optical interleaver with arbitrary bandwidth ratio and with the proposed structure can be obtained by controlling some key parameters. As an example, an asymmetrical interleaver with 12 interleaving ratio is presented, which can apportion 32.85 GHz and 67.15 GHz passband bandwidth for the 10 Gbit/s and 40 Gbit/s channels over 100 GHz channel spacing respectively. Therefore, the bandwidth efficiency requirement of the 40 Gbit/s channel is relieved. Furthermore, by analyzing the effect of optical power splitting ratio of the three two-mode interferometers on the output spectrum bandwidth ratio, the design instances of asymmetrical interleaver with different bandwidth ratios at the same channel space are given..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1105005 (2012)
Optical Design and Fabrication
Design of Optical System for Solar Extreme-Ultraviolet Imaging Spectrometer Using Holographic Varied Line Spacing Grating
Liu Zhuang, and Gong Yan
With the in-depth research in the physical process of solar activities, the demand for the performance of solar extreme-ultraviolet imaging spectrometer is increasing. One important method of designing high-performance sun extreme-ultraviolet imaging spectrometer is to use the holographic varied line spacing grating. TWith the in-depth research in the physical process of solar activities, the demand for the performance of solar extreme-ultraviolet imaging spectrometer is increasing. One important method of designing high-performance sun extreme-ultraviolet imaging spectrometer is to use the holographic varied line spacing grating. The design method is presented in this paper as follows. The initial optical structure of the system is designed firstly. Then the grating whose aberration is small is calculated based on holographic varied line spacing grating′s optical path difference theory and universal global optimization of 1stopt software. The entire system is modeled and optimized with optical design software Zemax finally. A design example is given with the working band of 17～21 nm, the field of view of 2400″, the spatial resolution of 0.6″, the spectral resolution of 0.00225 nm/pixel, and the length of about 2 m. In the spectral range, the root mean square radii in spatial direction and spectral direction and the modulation transfer function in the cutoff frequency range all satisfy the requirement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1116001 (2012)
Remote Sensing and Sensors
Fast Detection of Visual Saliency Regions in Remote Sensing Image based on Region Growing
Zhang Libao
The traditional visual attention model for the detection of visual saliency regions in the remote sensing image can lead to high computational complexity and low precision of detection. A new fast detection algorithm of visual saliency regions is proposed. The new algorithm firstly decreases the spatial resolution by iThe traditional visual attention model for the detection of visual saliency regions in the remote sensing image can lead to high computational complexity and low precision of detection. A new fast detection algorithm of visual saliency regions is proposed. The new algorithm firstly decreases the spatial resolution by integer wavelet transform, which can reduce the computational complexity of detection of the visual focus of attention. Then, the new algorithm proposes the two-dimensional discrete moment transform for visual feature fusion, which can generate the saliency map of the remote sensing image which has more abundant information of edge and texture. Finally, the region growing strategy based on the visual focus of attention is proposed in the saliency map analysis to acquire the precise contours of the visual saliency regions. The experimental results show that the new algorithm can not only effectively reduce the computational complexity of the detection of visual saliency regions in the remote sensing image, but also be able to accurately describe the contour information of visual saliency regions. In addition, it can avoid image segmentation and feature extraction for the whole image. The new algorithm provides a certain reference for the target detection of the remote sensing image in the future..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1114001 (2012)
A Photonic Crystal Fiber Temperature Sensor Based on Sagnac Interferometer Structure
Wu Tiesheng, Wang Li, Wang Zhe, Liu Yumin, Hu Shuyang, and Yin Lidan
A highly birefringent photonic crystal fiber loop mirror temperature sensor based on Sagnac interferometer structure is designed. As the photonic crystal fiber has good temperature stability, in order to achieve the temperature sensing, ethanol which has a high thermal coefficient is filled into the air holes of the hiA highly birefringent photonic crystal fiber loop mirror temperature sensor based on Sagnac interferometer structure is designed. As the photonic crystal fiber has good temperature stability, in order to achieve the temperature sensing, ethanol which has a high thermal coefficient is filled into the air holes of the high birefringence photonic crystal fiber. Using plane wave expansion method, the relationship between birefringence of the highly birefringent photonic crystal fiber and transmission wavelength, and that between birefringence and temperature are analyzed. Theoretical analysis shows that: filled with ethanol, the birefringence of high birefringence photonic crystal fiber increases with the increase of the transmission wavelength and temperature, besides, there is a linear relationship between birefringence and temperature. In the experiment, a piece of high birefringence photonic crystal fiber filled with ethanol is welded with a 3 dB coupler to form a fiber loop mirror. When the temperature rises from 45 ℃ to 80 ℃, the concave point drift of 309.280 nm towards the short wavelength is observed on spectrum analyzer. The sensitivity is as high as 8.837 nm/℃..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1114002 (2012)
Multi-View Point Cloud Scenes Mosaic Based on Projective Distribution Entropy
Tan Zhiguo, Lu Min, Guo Yulan, and Zuo Chao
Multi-view point cloud scenes mosaic is an effective method to solve the incomplete object data problem while self-occlusion and occlusion happened in ladar three dimensional imaging process. Mosaic method directly affects the object detection and recognition. By using projective distribution entropy, the independent cMulti-view point cloud scenes mosaic is an effective method to solve the incomplete object data problem while self-occlusion and occlusion happened in ladar three dimensional imaging process. Mosaic method directly affects the object detection and recognition. By using projective distribution entropy, the independent coordination of point cloud scene is estimated. Based on this, space transform parameters between multi-view point cloud scenes are calculated. Then, the annealing interative closet point (ICP) algorithm is used for precise mosaic. Experimental results demonstrate the effectiveness and feasibility of the proposed algorithm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1114003 (2012)
Spectroscopy
Raman Spectrum of Carbon Nanotubes Coated by Au Nano Particles Film
Zhang Jie, Chen Yulin, and Zhu Yong
A new structure based on carbon nanotubes and nano particles for Raman enhancement is presented. Experimental analysis is carried on. With chemical way, single-walled and multi-walled carbon nanotube films are obtained. Carbon nanotube film coated by Au nano particles samples are prepared with sputtering. Scanning elecA new structure based on carbon nanotubes and nano particles for Raman enhancement is presented. Experimental analysis is carried on. With chemical way, single-walled and multi-walled carbon nanotube films are obtained. Carbon nanotube film coated by Au nano particles samples are prepared with sputtering. Scanning electron microscope (SEM) image, reflectivity spectrum and Raman spectrum are measured. Experimental results indicate that the Raman intensity is enhanced due to Au nano particles function..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 11, 1115001 (2012)
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