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RSS2011 Vol. 35, No. 4
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2011, 35(4): 434-439.
doi: 10.3969/j.issn.1001-3806.2011.04.001
[Abstract]
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Abstract:
The progress of mid-infrared optical parametric oscillators(OPO)was reviewed,including the properties of the nonlinear crystals,technical parameters and OPO divice.The key issues and the development direction of the mid-infrared OPO were pointed out,and possible measures for performance development were put forward.
The progress of mid-infrared optical parametric oscillators(OPO)was reviewed,including the properties of the nonlinear crystals,technical parameters and OPO divice.The key issues and the development direction of the mid-infrared OPO were pointed out,and possible measures for performance development were put forward.
2011, 35(4): 440-443.
doi: 10.3969/j.issn.1001-3806.2011.04.002
Abstract:
In order to detect the laser welding seam surface defects of unequal-thickness steel blank,the structured light active vision method and Gaussian data fitting technology were used for the experiment research of the seam surface defects detection.Firstly,the laser strip center line in sub-pixel accuracy was extracted by Gaussian fitting.Secondly,the seam endpoint positions were obtained by line fitting and computing point of intersections of three lines.Thirdly,the computing methods of the surface defects of the laser welding seam,such as concavity,convexity,were put forward.The experiment result shows that the proposed method is based on structured light vision and data fitting is suit for laser welding seam detection of unequal-thickness steel blanks.
In order to detect the laser welding seam surface defects of unequal-thickness steel blank,the structured light active vision method and Gaussian data fitting technology were used for the experiment research of the seam surface defects detection.Firstly,the laser strip center line in sub-pixel accuracy was extracted by Gaussian fitting.Secondly,the seam endpoint positions were obtained by line fitting and computing point of intersections of three lines.Thirdly,the computing methods of the surface defects of the laser welding seam,such as concavity,convexity,were put forward.The experiment result shows that the proposed method is based on structured light vision and data fitting is suit for laser welding seam detection of unequal-thickness steel blanks.
2011, 35(4): 444-447,452.
doi: 10.3969/j.issn.1001-3806.2011.04.003
Abstract:
In order to improve the tribological properties of titanium alloy,a wear resistant coating with a microstructure consisting of insitu TiC primary dendrites and Ti-Ti2Co matrix was fabricated on a substrate of titanium alloy TC4 by means of laser cladding using Co-based alloy powders,activated carbon and titanium powders as the precursor materials.The microstructure and composition of the intermetallic composite coating was studied by means of optical microscope,scanning electron microscope,X-ray diffraction,energy dispersive spectrometer.The wear resistance of the coating was tested under dry sliding wear condition at room temperature.It is revealed that the laser clad composite coating has a rapidly solidified homogeneous microstructure and is metallurgically bonded to the substrate.The developed in situ TiC primary dendrites dispersed in the B-Ti-Ti2Co matrix of the coating as reinforcements.The B-Ti phase shows irregular crystal or cell dendrites.And most of the Ti2Co phase distributes over the matrix as irregular block crystal,with some lamellar Ti2Co formed in the inter-dendrite arms of the β-Ti phase.It is found that the microhardness of the coating is in the range of HV600～HV700.The laser clad TiC/ Ti-Ti2Co coating,in which the TiC phase plays a main role in enhancement,has excellent wear resistance under dry sliding wear test conditions.The results show that the coating is helpful to improve wear resistance of titanium alloy.
In order to improve the tribological properties of titanium alloy,a wear resistant coating with a microstructure consisting of insitu TiC primary dendrites and Ti-Ti2Co matrix was fabricated on a substrate of titanium alloy TC4 by means of laser cladding using Co-based alloy powders,activated carbon and titanium powders as the precursor materials.The microstructure and composition of the intermetallic composite coating was studied by means of optical microscope,scanning electron microscope,X-ray diffraction,energy dispersive spectrometer.The wear resistance of the coating was tested under dry sliding wear condition at room temperature.It is revealed that the laser clad composite coating has a rapidly solidified homogeneous microstructure and is metallurgically bonded to the substrate.The developed in situ TiC primary dendrites dispersed in the B-Ti-Ti2Co matrix of the coating as reinforcements.The B-Ti phase shows irregular crystal or cell dendrites.And most of the Ti2Co phase distributes over the matrix as irregular block crystal,with some lamellar Ti2Co formed in the inter-dendrite arms of the β-Ti phase.It is found that the microhardness of the coating is in the range of HV600～HV700.The laser clad TiC/ Ti-Ti2Co coating,in which the TiC phase plays a main role in enhancement,has excellent wear resistance under dry sliding wear test conditions.The results show that the coating is helpful to improve wear resistance of titanium alloy.
2011, 35(4): 448-452.
doi: 10.3969/j.issn.1001-3806.2011.04.004
Abstract:
Laser cladding is an important new technology of material modification and has a good prospect.With the improvement of mechanical strength,low thickness of the cladding layer can not meet the performance requirements,so laser cladding trends to prepare the high thickness coating.Now,the single and multi-layer laser cladding techniques are the main measures to achieve the high thickness coating,and the multi-layer laser cladding is divided into a constant chemical composition multi-layer cladding (CCCMLC) and functionally gradient material multi-layer cladding (FGMMLC).The research status of high thickness coating by single-layer and multi-layer laser cladding and highlights status of the FGMMLC were summarized.Finally, the development trend of the technology in the future was prospected.
Laser cladding is an important new technology of material modification and has a good prospect.With the improvement of mechanical strength,low thickness of the cladding layer can not meet the performance requirements,so laser cladding trends to prepare the high thickness coating.Now,the single and multi-layer laser cladding techniques are the main measures to achieve the high thickness coating,and the multi-layer laser cladding is divided into a constant chemical composition multi-layer cladding (CCCMLC) and functionally gradient material multi-layer cladding (FGMMLC).The research status of high thickness coating by single-layer and multi-layer laser cladding and highlights status of the FGMMLC were summarized.Finally, the development trend of the technology in the future was prospected.
2011, 35(4): 453-456,476.
doi: 10.3969/j.issn.1001-3806.2011.04.005
Abstract:
In order to investigate the effect of different welding parameters on the welding width and depth,the mathematical and finite element model of plastic transmission welding were proposed,and the welding temperature distribution was calculated by means of ANSYS,and the welding width and depth for different parameters was predicted.The results show that the welding depth increases with increasing of the laser energy absorbed by polymethyl methacrylate (PMMA) in a unit area and unit time,the welding width is affected by the laser diameter and the laser energy absorbed by PMMA in a unit area and unit time,and the welding depth increases firstly and then decreases with the laser diameter increasing.
In order to investigate the effect of different welding parameters on the welding width and depth,the mathematical and finite element model of plastic transmission welding were proposed,and the welding temperature distribution was calculated by means of ANSYS,and the welding width and depth for different parameters was predicted.The results show that the welding depth increases with increasing of the laser energy absorbed by polymethyl methacrylate (PMMA) in a unit area and unit time,the welding width is affected by the laser diameter and the laser energy absorbed by PMMA in a unit area and unit time,and the welding depth increases firstly and then decreases with the laser diameter increasing.
2011, 35(4): 457-460,467.
doi: 10.3969/j.issn.1001-3806.2011.04.006
Abstract:
A wear resistant Cr7C3 reinforced Cr-Ni-Si ternary metal silicide composite coating was fabricated on a substrate of A3 mild steel by means of laser cladding with Cr3C2 and 0.47Cr-0.50Ni-0.03Si alloy powder as the precursor material.The microstructure and composition of the coating were investigated by means of optical microscopy,scanning electron microscopy,Xray diffraction,energy dispersive spectrometer and electron probe micro-analyzer.Then the wear resistance of the coating was tested under dry sliding wear condition at room temperature.Results indicated that,microhardness of the Cr-Ni-Si coating was evidently improved because of the introduction of Cr7C3.The laser clad Cr7C3 reinforced Cr-Ni-Si ternary metal silicide composite coating shows excellent wear resistance under dry sliding wear test conditions.
A wear resistant Cr7C3 reinforced Cr-Ni-Si ternary metal silicide composite coating was fabricated on a substrate of A3 mild steel by means of laser cladding with Cr3C2 and 0.47Cr-0.50Ni-0.03Si alloy powder as the precursor material.The microstructure and composition of the coating were investigated by means of optical microscopy,scanning electron microscopy,Xray diffraction,energy dispersive spectrometer and electron probe micro-analyzer.Then the wear resistance of the coating was tested under dry sliding wear condition at room temperature.Results indicated that,microhardness of the Cr-Ni-Si coating was evidently improved because of the introduction of Cr7C3.The laser clad Cr7C3 reinforced Cr-Ni-Si ternary metal silicide composite coating shows excellent wear resistance under dry sliding wear test conditions.
2011, 35(4): 461-467.
doi: 10.3969/j.issn.1001-3806.2011.04.007
Abstract:
The incorporation of inorganic nanoparticles into photopolymer is a new way to produce organic-inorganic hybrid photopolymer holographic storage material.The progress from the conventional all-organic type to the organic-inorganic photopolymer was introduced.The nanoparticles uniformly dispersed in all-organic photopolymer significantly improve the performance of holographic recording material.The potential application advantages and the prospect of organic-inorganic hybrid photopolymer were forecasted.
The incorporation of inorganic nanoparticles into photopolymer is a new way to produce organic-inorganic hybrid photopolymer holographic storage material.The progress from the conventional all-organic type to the organic-inorganic photopolymer was introduced.The nanoparticles uniformly dispersed in all-organic photopolymer significantly improve the performance of holographic recording material.The potential application advantages and the prospect of organic-inorganic hybrid photopolymer were forecasted.
2011, 35(4): 468-471.
doi: 10.3969/j.issn.1001-3806.2011.04.008
Abstract:
For effectively detecting the backscattering optical wake flow signal from the noise,the collected original signal was transferred into one dimension discrete wavelets based on four Daubechies wavelet decomposition (db4WD) so that the low frequency term,indicating the backscattered signal from the shake waves,was distinguished from the high frequency terms, indicating noise.Then,the wavelet coefficients were obtained based on the threshold function.A new threshold function was put forward on the basis of wavelet soft and hard threshold de-noising method with entropies indicating the sparsity distribution of the original signal data.The new function can not only overcome discontinuity disadvantage of the hard threshold function,but also solve constant deviation in the soft threshold function.The new threshold function can effectively eliminate noise and overcome the disadvantage of soft and hard threshold function so that good results can be obtained.
For effectively detecting the backscattering optical wake flow signal from the noise,the collected original signal was transferred into one dimension discrete wavelets based on four Daubechies wavelet decomposition (db4WD) so that the low frequency term,indicating the backscattered signal from the shake waves,was distinguished from the high frequency terms, indicating noise.Then,the wavelet coefficients were obtained based on the threshold function.A new threshold function was put forward on the basis of wavelet soft and hard threshold de-noising method with entropies indicating the sparsity distribution of the original signal data.The new function can not only overcome discontinuity disadvantage of the hard threshold function,but also solve constant deviation in the soft threshold function.The new threshold function can effectively eliminate noise and overcome the disadvantage of soft and hard threshold function so that good results can be obtained.
2011, 35(4): 472-476.
doi: 10.3969/j.issn.1001-3806.2011.04.009
Abstract:
In order to cut liquid crystal display (LCD) glass substrates with controlled crack,a new method was put forward.Firstly,an initial crack was prepared on the surface of LCD substrates with Nd: YAG laser.Then,the substrate was heated up with CO2 laser and cooled with Ar gas.The effect of laser spot size and the thickness of LCD glass substrates on laser cutting quality was analyzed.The surface and performance of the cutting face after laser treatment was tested by means of scanning electronic microscope (SEM).The cutting quality was compared with the traditional mechanical cutting quality.The results show that there are lots of micro cracks in the substrates cut with traditional mechanical method,however,the laser cutting surface based on thermal cracking method is smooth and flat,no micro cracks exists,and the cutting section-affecting zone is less than 20μm.It is better to cut LCD glass substrates with thermal crack laser cutting method than mechanical cutting method.
In order to cut liquid crystal display (LCD) glass substrates with controlled crack,a new method was put forward.Firstly,an initial crack was prepared on the surface of LCD substrates with Nd: YAG laser.Then,the substrate was heated up with CO2 laser and cooled with Ar gas.The effect of laser spot size and the thickness of LCD glass substrates on laser cutting quality was analyzed.The surface and performance of the cutting face after laser treatment was tested by means of scanning electronic microscope (SEM).The cutting quality was compared with the traditional mechanical cutting quality.The results show that there are lots of micro cracks in the substrates cut with traditional mechanical method,however,the laser cutting surface based on thermal cracking method is smooth and flat,no micro cracks exists,and the cutting section-affecting zone is less than 20μm.It is better to cut LCD glass substrates with thermal crack laser cutting method than mechanical cutting method.
2011, 35(4): 477-480,542.
doi: 10.3969/j.issn.1001-3806.2011.04.010
Abstract:
In order to investigate the damage induced by ms laser,the experiment installation was established according to ISO-11254 and GB/T-16601.The 1064nm laser-induced damage thresholds of Ti2/Si2 coatings at lms and 10ns pulse-widths were studied,and the damage photos,damage depth,damage radius and damage mechanisms were also investigated.The damage of the coatings induced by ms laser was compared with that induced by ns laser.The damage threshold of energy density induced by ms laser is one order of magnitude higher than that of 10ns laser,and the damage threshold of power density induced by ms laser is one ten-thousandth of that of 10ns laser.The damage radius induced by ms laser is 180μm longer than that induced by ns laser,and the damage depth is 200μm deeper.It could be concluded that 1ms laser induced damage of optical coatings is more severe,it not only damage the coating but also destroy the substrate of the coating.The results provide important references for the researches of damage induced laser with pulse duration at millisecond scale.
In order to investigate the damage induced by ms laser,the experiment installation was established according to ISO-11254 and GB/T-16601.The 1064nm laser-induced damage thresholds of Ti2/Si2 coatings at lms and 10ns pulse-widths were studied,and the damage photos,damage depth,damage radius and damage mechanisms were also investigated.The damage of the coatings induced by ms laser was compared with that induced by ns laser.The damage threshold of energy density induced by ms laser is one order of magnitude higher than that of 10ns laser,and the damage threshold of power density induced by ms laser is one ten-thousandth of that of 10ns laser.The damage radius induced by ms laser is 180μm longer than that induced by ns laser,and the damage depth is 200μm deeper.It could be concluded that 1ms laser induced damage of optical coatings is more severe,it not only damage the coating but also destroy the substrate of the coating.The results provide important references for the researches of damage induced laser with pulse duration at millisecond scale.
2011, 35(4): 481-485,491.
doi: 10.3969/j.issn.1001-3806.2011.04.011
Abstract:
In order to get the more exact profile of horizontal wind speed,the wind field was measured with the first domestic Rayleigh Doppler wind lidar based on a triple Fabry-Perot etalon,a method was brought up to retrieve the laser frequency in which the location of the etalon was adjusted in time according to the real detected data.The errors caused by the jitter and drift of the laser can be effectively reduced by means of this wind inversion algorithm.In addition,improving the traditional method,a nonlinear iteration inversion method was proposed.After processing the same Monte-Carlo simulated data with both the methods,it was found that the nonlinear iteration inversion method had a better precision.The profile of horizontal wind speed from 10km to 40km was obtained after processing the Rayleigh Doppler wind lidar signal data by means of the nonlinear iteration inversion method.The results show that this inversion method is feasible,and can effectively improve the inversion precision.
In order to get the more exact profile of horizontal wind speed,the wind field was measured with the first domestic Rayleigh Doppler wind lidar based on a triple Fabry-Perot etalon,a method was brought up to retrieve the laser frequency in which the location of the etalon was adjusted in time according to the real detected data.The errors caused by the jitter and drift of the laser can be effectively reduced by means of this wind inversion algorithm.In addition,improving the traditional method,a nonlinear iteration inversion method was proposed.After processing the same Monte-Carlo simulated data with both the methods,it was found that the nonlinear iteration inversion method had a better precision.The profile of horizontal wind speed from 10km to 40km was obtained after processing the Rayleigh Doppler wind lidar signal data by means of the nonlinear iteration inversion method.The results show that this inversion method is feasible,and can effectively improve the inversion precision.
2011, 35(4): 486-491.
doi: 10.3969/j.issn.1001-3806.2011.04.012
Abstract:
To achieve effective protection against laser and microwave radiation,the compound technologies incorporating laser and microwave protection and laser warning were studied and this kind of multifunction protection goggles were designed. The key technologies include multifunction protection materials and compounded technology,sandwich type lenses compounded technology by means of heat press in vacuum,eye protection technology of resisting the splash induced by impact,adjustable protection eyeglasses technology between separated type and combined type.Multifunction protection performances of the developed protection goggles were tested.In addition,environment adaptability,laser biology effect and human-machine work efficiency were tested.The optical characteristics and compound technologies of multifunction integration protection goggles as well as relative techniques parameters were introduced.The experimental results show that ultraviolet transmittance of multifunction protection goggles is 0.0003～0.0005; relatively deviation of optical density of the goggles passing environment test and stored for 10 years is 0.0024～0.035; non-uniformity of optical density of the spectacles is 0.00059～0.0011;relatively deviation of optical density of the spectacles at laser incident angle of 0°～30° is 0.0061～0.012; relatively deviation of optical density of the spectacles at laser incident angle of 0°～30° is 0.0019～0.014 for laser exposure at different polarization directions; rabbit eyes wearing with the spectacles were not damaged at laser radiant exposure of(578.5～2405)mJ·cm-2.All performance indexes of this goggles accord with the demands of design and application.The multifunction protection goggles have good protective effect and can be used in the science research,teaching,manufacture,training and medical treatment.
To achieve effective protection against laser and microwave radiation,the compound technologies incorporating laser and microwave protection and laser warning were studied and this kind of multifunction protection goggles were designed. The key technologies include multifunction protection materials and compounded technology,sandwich type lenses compounded technology by means of heat press in vacuum,eye protection technology of resisting the splash induced by impact,adjustable protection eyeglasses technology between separated type and combined type.Multifunction protection performances of the developed protection goggles were tested.In addition,environment adaptability,laser biology effect and human-machine work efficiency were tested.The optical characteristics and compound technologies of multifunction integration protection goggles as well as relative techniques parameters were introduced.The experimental results show that ultraviolet transmittance of multifunction protection goggles is 0.0003～0.0005; relatively deviation of optical density of the goggles passing environment test and stored for 10 years is 0.0024～0.035; non-uniformity of optical density of the spectacles is 0.00059～0.0011;relatively deviation of optical density of the spectacles at laser incident angle of 0°～30° is 0.0061～0.012; relatively deviation of optical density of the spectacles at laser incident angle of 0°～30° is 0.0019～0.014 for laser exposure at different polarization directions; rabbit eyes wearing with the spectacles were not damaged at laser radiant exposure of(578.5～2405)mJ·cm-2.All performance indexes of this goggles accord with the demands of design and application.The multifunction protection goggles have good protective effect and can be used in the science research,teaching,manufacture,training and medical treatment.
2011, 35(4): 492-494.
doi: 10.3969/j.issn.1001-3806.2011.04.013
Abstract:
In order to study effect of the silica ring at the core-cladding interface on the transmission bandwidth,dispersion, core-confined energy and nonlinear coefficient,for the designed 7-cell hollow-core photonic bandgap fibers(HC-PBGFs),they were numerically simulated by means of full-vector finite element method,and the curves of the transmission bandwidth, dispersion,core-confined energy,nonlinear coefficient in different normalized thickness of the silica ring with the same core radius were obtained.The simulation results show that the best range of normalized thickness of silica ring is 0.5 to 0.6,which provides theoretical evidence to design the HC-PBGFs.
In order to study effect of the silica ring at the core-cladding interface on the transmission bandwidth,dispersion, core-confined energy and nonlinear coefficient,for the designed 7-cell hollow-core photonic bandgap fibers(HC-PBGFs),they were numerically simulated by means of full-vector finite element method,and the curves of the transmission bandwidth, dispersion,core-confined energy,nonlinear coefficient in different normalized thickness of the silica ring with the same core radius were obtained.The simulation results show that the best range of normalized thickness of silica ring is 0.5 to 0.6,which provides theoretical evidence to design the HC-PBGFs.
2011, 35(4): 495-498.
doi: 10.3969/j.issn.1001-3806.2011.04.014
Abstract:
In order to study the ultraviolet communication characteristics accurately and comprehensively so that it can be adopted in actual 3-D space application,with the height information synthesized in the single scattering link model,the error was computed with the height information or not.The result shows that potential interference of height on the transmitting angle and receiving angle will lead to receiving power changes,even lead to communication failure under some circumstances.Thus,it provides a good guideline to real application of the ultraviolet communication settings.
In order to study the ultraviolet communication characteristics accurately and comprehensively so that it can be adopted in actual 3-D space application,with the height information synthesized in the single scattering link model,the error was computed with the height information or not.The result shows that potential interference of height on the transmitting angle and receiving angle will lead to receiving power changes,even lead to communication failure under some circumstances.Thus,it provides a good guideline to real application of the ultraviolet communication settings.
2011, 35(4): 499-502.
doi: 10.3969/j.issn.1001-3806.2011.04.015
Abstract:
In order to study the quantum effect and defect mode of light wave in 1-D anisotropic rectangle doping photonic crystal,the quantum effect was calculated by means of characteristic matrix and the defect mode characteristics of TE wave and TM wave were calculated.New defect mode structure of 1-D anisotropic rectangle doping photonic crystal was obtained.The results show that the defect mode frequency and transmission angle increases with increasing quantum number.The defect mode frequency of the same pattern decreases with increasing rectangle side length.
In order to study the quantum effect and defect mode of light wave in 1-D anisotropic rectangle doping photonic crystal,the quantum effect was calculated by means of characteristic matrix and the defect mode characteristics of TE wave and TM wave were calculated.New defect mode structure of 1-D anisotropic rectangle doping photonic crystal was obtained.The results show that the defect mode frequency and transmission angle increases with increasing quantum number.The defect mode frequency of the same pattern decreases with increasing rectangle side length.
2011, 35(4): 503-510.
doi: 10.3969/j.issn.1001-3806.2011.04.016
Abstract:
The fundamental and measurement principles of tunable diode laser absorption spectroscopy (TDLAS) for combustion diagnostics were introduced.The characteristics and problems of TDLAS systems based on time division multiplexing (TDM),wavelength division multiplexing (WDM),a single laser,velocity and mass flux sensor and tunable diode laser absorption tomography were also referred.Furthermore,the development history and latest applications of TDLAS were summarized,and the developing trend was discussed.
The fundamental and measurement principles of tunable diode laser absorption spectroscopy (TDLAS) for combustion diagnostics were introduced.The characteristics and problems of TDLAS systems based on time division multiplexing (TDM),wavelength division multiplexing (WDM),a single laser,velocity and mass flux sensor and tunable diode laser absorption tomography were also referred.Furthermore,the development history and latest applications of TDLAS were summarized,and the developing trend was discussed.
2011, 35(4): 511-513,517.
doi: 10.3969/j.issn.1001-3806.2011.04.017
Abstract:
In order to strengthen the vibration resistance of the optical system in actual applications and improve the beam quality and direction stability,taking optimal design of optical components as an example,a simulation platform was built with Visual Basic(VB)and MATLAB to develop ANSYS.Firstly,the parameters were modeled and the main control interface was developed with VB.Secondly,the structure was optimized and calculated by means of ANSYS.Finally,the animation image data were generated in real time and visually displayed based on MATLAB.Hence,the optimization of optical components design process becomes more intuitive and convenient.It is helpful to analyze and evaluate anti-vibration performance of the optical element.
In order to strengthen the vibration resistance of the optical system in actual applications and improve the beam quality and direction stability,taking optimal design of optical components as an example,a simulation platform was built with Visual Basic(VB)and MATLAB to develop ANSYS.Firstly,the parameters were modeled and the main control interface was developed with VB.Secondly,the structure was optimized and calculated by means of ANSYS.Finally,the animation image data were generated in real time and visually displayed based on MATLAB.Hence,the optimization of optical components design process becomes more intuitive and convenient.It is helpful to analyze and evaluate anti-vibration performance of the optical element.
2011, 35(4): 514-517.
doi: 10.3969/j.issn.1001-3806.2011.04.018
Abstract:
Cholesteric liquid crystal lasers have been extensively studied but barely studied in our country.The periodic helical structure and selective reflection property of cholesteric liquid crystal were introduced.The principle and research progress of cholesteric liquid crystal based lasers and its potential applications were reviewed to provide some reference for the specialists in our country.
Cholesteric liquid crystal lasers have been extensively studied but barely studied in our country.The periodic helical structure and selective reflection property of cholesteric liquid crystal were introduced.The principle and research progress of cholesteric liquid crystal based lasers and its potential applications were reviewed to provide some reference for the specialists in our country.
2011, 35(4): 518-521.
doi: 10.3969/j.issn.1001-3806.2011.04.019
Abstract:
In order to study the noise characteristics of image frame sequence in a range-gated underwater laser imaging system,the method of 3-D noise analysis was adopted.In order to solve the problem of non-uniformity and sample inadequacy of the experimental data sets,simulated data set was composed of synthesized noise images produced according to single image frame.The calculation results of 3-D noise analysis based on the simulated data set and experimental data set were compared, which showed that the instant pixel noise describing the random variety along three directions was the main noise source in rangegated underwater laser image sequence and the effect of temporal noise was more severe than the spatial noise.Those results are helpful in the design of range-gated underwater laser imaging system and image denoising algorithm.
In order to study the noise characteristics of image frame sequence in a range-gated underwater laser imaging system,the method of 3-D noise analysis was adopted.In order to solve the problem of non-uniformity and sample inadequacy of the experimental data sets,simulated data set was composed of synthesized noise images produced according to single image frame.The calculation results of 3-D noise analysis based on the simulated data set and experimental data set were compared, which showed that the instant pixel noise describing the random variety along three directions was the main noise source in rangegated underwater laser image sequence and the effect of temporal noise was more severe than the spatial noise.Those results are helpful in the design of range-gated underwater laser imaging system and image denoising algorithm.
2011, 35(4): 522-526,530.
doi: 10.3969/j.issn.1001-3806.2011.04.020
Abstract:
In order to analyze the effect of different parameters on the rigid photovoltaic spatial solitons formed in two-photon photorefractive medium,the evolution equation of such solitons was deduced.According to the practical condition,after the equation was simplified based on approximation,its analytical solutions were obtained,and the effect of different parameters, such as photovoltaic field,dark background radiation,start light,absorption coefficient,and wavelength,on these solitons were also discussed.Results show that with the intensity of photovoltaic field increasing,the full width at half maxim of solitons decreases accordingly and with the other parameters increasing,the full width at half maxim of solitons increases accordingly just at different increasing rates.It turned out that this study results provide theoretic basis for development of the spatial solitons theory.
In order to analyze the effect of different parameters on the rigid photovoltaic spatial solitons formed in two-photon photorefractive medium,the evolution equation of such solitons was deduced.According to the practical condition,after the equation was simplified based on approximation,its analytical solutions were obtained,and the effect of different parameters, such as photovoltaic field,dark background radiation,start light,absorption coefficient,and wavelength,on these solitons were also discussed.Results show that with the intensity of photovoltaic field increasing,the full width at half maxim of solitons decreases accordingly and with the other parameters increasing,the full width at half maxim of solitons increases accordingly just at different increasing rates.It turned out that this study results provide theoretic basis for development of the spatial solitons theory.
2011, 35(4): 527-530.
doi: 10.3969/j.issn.1001-3806.2011.04.021
Abstract:
To extract urban digital terrain model (DTM) from airborne laser scanning data,a filtering algorithm was proposed after analyzing the multi-pulse characteristics of urban airborne light detection and ranging (LIDAR) data.In this method,according to the distribution characteristics of urban airborne LIDAR data,laser footprints were distributed into voxels with proper volume,then object points were excluded and terrain points were reserved on the basis of filtering rules.Finally,the experiment result shows that this method can extract DTM more effectively.Meanwhile,the calculation amount is reduced during data processing which is helpful for improving computation efficiency of the mass LIDAR data.
To extract urban digital terrain model (DTM) from airborne laser scanning data,a filtering algorithm was proposed after analyzing the multi-pulse characteristics of urban airborne light detection and ranging (LIDAR) data.In this method,according to the distribution characteristics of urban airborne LIDAR data,laser footprints were distributed into voxels with proper volume,then object points were excluded and terrain points were reserved on the basis of filtering rules.Finally,the experiment result shows that this method can extract DTM more effectively.Meanwhile,the calculation amount is reduced during data processing which is helpful for improving computation efficiency of the mass LIDAR data.
2011, 35(4): 531-534,538.
doi: 10.3969/j.issn.1001-3806.2011.04.022
Abstract:
In order to reduce burst loss probability and guarantee the quality of service (QoS) of optical burst switching(OBS)networks efficiently,a preemption window mechanism based on priority in emulated-OBS networks was proposed,in which a preemption window was set in the control channel of the emulated-OBS core routers to determine whether or not to allow high-priority bursts to preempt low-priority bursts.When competition occurs,the system estimates whether the arrival time of high-priority bursts corresponding to control bursts meets the preemption condition.If the preemption condition is satisfied,highpriority bursts are allowed to preempt low-priority bursts.Otherwise,preemption is not allowed.The theoretical analysis and the simulation experiment of this mechanism were carried out,and a series of data how the loss probability of the different priority bursts changing with the preemption window time in the different channel systems were obtained.Simulation results show that the mechanism can efficiently reduce the burst loss probability of high-priority bursts,and the burst loss probability of the highpriority bursts is much less than that of the low-priority bursts.The QoS of OBS networks is guaranteed by this mechanism. Hence,the scheme can efficiently improve the performance of OBS networks.
In order to reduce burst loss probability and guarantee the quality of service (QoS) of optical burst switching(OBS)networks efficiently,a preemption window mechanism based on priority in emulated-OBS networks was proposed,in which a preemption window was set in the control channel of the emulated-OBS core routers to determine whether or not to allow high-priority bursts to preempt low-priority bursts.When competition occurs,the system estimates whether the arrival time of high-priority bursts corresponding to control bursts meets the preemption condition.If the preemption condition is satisfied,highpriority bursts are allowed to preempt low-priority bursts.Otherwise,preemption is not allowed.The theoretical analysis and the simulation experiment of this mechanism were carried out,and a series of data how the loss probability of the different priority bursts changing with the preemption window time in the different channel systems were obtained.Simulation results show that the mechanism can efficiently reduce the burst loss probability of high-priority bursts,and the burst loss probability of the highpriority bursts is much less than that of the low-priority bursts.The QoS of OBS networks is guaranteed by this mechanism. Hence,the scheme can efficiently improve the performance of OBS networks.
2011, 35(4): 539-542.
doi: 10.3969/j.issn.1001-3806.2011.04.024
Abstract:
In order to study multiplexers,the design and implementation of coalition of multi-route data and voice based on free space optical communication (FSO) was introduced.Combining FSO technical advantages with telephone line transmission system,the compound interface between digital signal and voice was implemented based on field programmable gate array (FPGA). The FPGA was programmed with Verilog hardware description language (HDL),and the whole trajectory was simulated with QUARTUSⅡsoftware.As a result,the channel efficiency was promoted and the transfer capacity was increased because of the capability of digital multiple connection.The results show that the system is able to transfer 30-channel audio signal.
In order to study multiplexers,the design and implementation of coalition of multi-route data and voice based on free space optical communication (FSO) was introduced.Combining FSO technical advantages with telephone line transmission system,the compound interface between digital signal and voice was implemented based on field programmable gate array (FPGA). The FPGA was programmed with Verilog hardware description language (HDL),and the whole trajectory was simulated with QUARTUSⅡsoftware.As a result,the channel efficiency was promoted and the transfer capacity was increased because of the capability of digital multiple connection.The results show that the system is able to transfer 30-channel audio signal.
2011, 35(4): 543-546,550.
doi: 10.3969/j.issn.1001-3806.2011.04.025
Abstract:
In order to improve the beam quality of a two-side-pumped symmetrically transverse flow continuous liquid laser, the output beam quality M2 factor and light intensity distribution at different flow velocities were simulated on the condition of the liquid laser pumped symmetrically with two sides diode lasers,the heat distribution in the liquid medium was analyzed by means of ANSYS software.Simulation results show that is an optimum flow velocity for best beam quality.For both the gain and refractive index in the laser system distribute symmetrically with the pumping direction,after compensation for the wavefront error with cylindrical lenses,the M2 factor was decreased from 24 to 12.5.
In order to improve the beam quality of a two-side-pumped symmetrically transverse flow continuous liquid laser, the output beam quality M2 factor and light intensity distribution at different flow velocities were simulated on the condition of the liquid laser pumped symmetrically with two sides diode lasers,the heat distribution in the liquid medium was analyzed by means of ANSYS software.Simulation results show that is an optimum flow velocity for best beam quality.For both the gain and refractive index in the laser system distribute symmetrically with the pumping direction,after compensation for the wavefront error with cylindrical lenses,the M2 factor was decreased from 24 to 12.5.
2011, 35(4): 547-550.
doi: 10.3969/j.issn.1001-3806.2011.04.026
Abstract:
Based on the mathematical model of photodynamic-damage dose in tumor and the function of photodynamicdamage dose with light dose,photosensitizer dose and oxygen concentration,the relationship of effective absorbed dose of light and photosensitizer changed with oxygen concentration was studied,then the photodynamic-damage effects of K562 cells on different medicine(light and photosensitizer) dose was presented.It is found that there is an optimal therapeutic dose during photodynamic therapy (PDT)and its size related with oxygen concentration,the severer the hypoxia,the smaller the optimal photodynamic dose and the less the tumor is damaged.In experiments it was found that the optimal dose in K562 cells suspension was 20 ×0.25 (J/cm2×mmol/L) when the photodynamic damage effect was best.It is shown that tumor can be damaged selectively in PDT and it provides a theoretical support for PDT to be widely used in clinics.
Based on the mathematical model of photodynamic-damage dose in tumor and the function of photodynamicdamage dose with light dose,photosensitizer dose and oxygen concentration,the relationship of effective absorbed dose of light and photosensitizer changed with oxygen concentration was studied,then the photodynamic-damage effects of K562 cells on different medicine(light and photosensitizer) dose was presented.It is found that there is an optimal therapeutic dose during photodynamic therapy (PDT)and its size related with oxygen concentration,the severer the hypoxia,the smaller the optimal photodynamic dose and the less the tumor is damaged.In experiments it was found that the optimal dose in K562 cells suspension was 20 ×0.25 (J/cm2×mmol/L) when the photodynamic damage effect was best.It is shown that tumor can be damaged selectively in PDT and it provides a theoretical support for PDT to be widely used in clinics.
2011, 35(4): 551-553,558.
doi: 10.3969/j.issn.1001-3806.2011.04.027
Abstract:
In order to study the diffuse transmission influence of laser acupuncture with different surface distribution light sources,the image-point-source distribution on meridian tissue is analyzed and diffusion equation of the image-point-source is solved through the use of extrapolation boundary conditions and Green response.Diffuse output models in acupuncture region for different distribution surface light source are obtained by a series responses of virtual points source.Flat,fiber and gauss acupuncture laser are simulated by Monte-Carlo method.The results indicated that; (1) the radial light energy in three acupuncture without spot mainly was concentrated in the near light source region and coincided when the radial distance to more than 0.135 cm,and axial light energy showed a negative exponential decay in flat and gauss acupuncture and linear decline in fiber source; (2) when surface light source existed circular or ring spot,the diffuse was inversely proportional to the spot area, especially the diffuse of circular spot being larger than the ring spot under the same spot area,and diffuse reflectance curve had a significant distortion at the vertical projection and was inversely proportional to the distance outside the projection,especially when the distance to 0.5 times of the spot radius the curve distortion being basically eliminated.The results may provide a useful reference for light source selection and acupuncture location of acupuncture points.
In order to study the diffuse transmission influence of laser acupuncture with different surface distribution light sources,the image-point-source distribution on meridian tissue is analyzed and diffusion equation of the image-point-source is solved through the use of extrapolation boundary conditions and Green response.Diffuse output models in acupuncture region for different distribution surface light source are obtained by a series responses of virtual points source.Flat,fiber and gauss acupuncture laser are simulated by Monte-Carlo method.The results indicated that; (1) the radial light energy in three acupuncture without spot mainly was concentrated in the near light source region and coincided when the radial distance to more than 0.135 cm,and axial light energy showed a negative exponential decay in flat and gauss acupuncture and linear decline in fiber source; (2) when surface light source existed circular or ring spot,the diffuse was inversely proportional to the spot area, especially the diffuse of circular spot being larger than the ring spot under the same spot area,and diffuse reflectance curve had a significant distortion at the vertical projection and was inversely proportional to the distance outside the projection,especially when the distance to 0.5 times of the spot radius the curve distortion being basically eliminated.The results may provide a useful reference for light source selection and acupuncture location of acupuncture points.
2011, 35(4): 554-558.
doi: 10.3969/j.issn.1001-3806.2011.04.028
Abstract:
In order to escape unsuccessful initiation from non-integrity of the optical path in a laser initiation system,both autocorrelation detection and cross-correlation detection were designed and compared.The experimental results show that the lowest detectable power of echo signal of laser initiator feedback fiber is 100nw for autocorrelation detection,0.1mw for crosscorrelation detection respectively.When the laser power is less than 0.2mw,the integrity of the optical path can be detected with cross-correlation detection,but cannot with autocorrelation detection.
In order to escape unsuccessful initiation from non-integrity of the optical path in a laser initiation system,both autocorrelation detection and cross-correlation detection were designed and compared.The experimental results show that the lowest detectable power of echo signal of laser initiator feedback fiber is 100nw for autocorrelation detection,0.1mw for crosscorrelation detection respectively.When the laser power is less than 0.2mw,the integrity of the optical path can be detected with cross-correlation detection,but cannot with autocorrelation detection.
2011, 35(4): 559-561,565.
doi: 10.3969/j.issn.1001-3806.2011.04.029
Abstract:
In order to obtain the rule of polarization measurement error caused by the phenomena of convergent light in a polarization camera,based on three dimensional polarization ray tracing calculi,the effect of transmitted polarized intensity parallel to optical axis on the measurement accuracy of polarization degree was studied.Simulation results show that the measured degree of polarization is always less than the real polarization degree due to the convergence of light,and polarization measurement error increases with the convergent angular.It is also indicated that for a certain light convergent state and polarization measurement condition,the larger the polarization degree of incident light,the bigger the polarization measurement error.
In order to obtain the rule of polarization measurement error caused by the phenomena of convergent light in a polarization camera,based on three dimensional polarization ray tracing calculi,the effect of transmitted polarized intensity parallel to optical axis on the measurement accuracy of polarization degree was studied.Simulation results show that the measured degree of polarization is always less than the real polarization degree due to the convergence of light,and polarization measurement error increases with the convergent angular.It is also indicated that for a certain light convergent state and polarization measurement condition,the larger the polarization degree of incident light,the bigger the polarization measurement error.
2011, 35(4): 562-565.
doi: 10.3969/j.issn.1001-3806.2011.04.030
Abstract:
In order to analyze the focal switch phenomena of cosine-squared Gaussian beams passing through an astigmatic lens,the expression for the axial irradiance distribution of focused cosine-squared Gaussian beams was derived based on the Collins formula.By means of numerical calculation,effect of astigmatic parameter on the axial irradiance was obtained.The dependence of the relative focal shift on the astigmatic parameter was studied at different positions of the beam's incident plane for a particular beam parameter and Fresnel number; the range of the beam's incident position of dual focal switches under this condition was determined and the focal switch due to the astigmatism was interpreted.
In order to analyze the focal switch phenomena of cosine-squared Gaussian beams passing through an astigmatic lens,the expression for the axial irradiance distribution of focused cosine-squared Gaussian beams was derived based on the Collins formula.By means of numerical calculation,effect of astigmatic parameter on the axial irradiance was obtained.The dependence of the relative focal shift on the astigmatic parameter was studied at different positions of the beam's incident plane for a particular beam parameter and Fresnel number; the range of the beam's incident position of dual focal switches under this condition was determined and the focal switch due to the astigmatism was interpreted.
2011, 35(4): 566-569,572.
doi: 10.3969/j.issn.1001-3806.2011.04.031
Abstract:
In order to study property of prohibit band gaps in 1-D ternary unmagnetized plasma photonic crystals,the transfer matrix method was applied to simulate the electromagnetic wave propagation through 1-D ternary unmagnetized plasma photonic crystals.Based on the calculated transmission coefficients,effect of periodic constant,dielectric constant,thickness of dielectric layer and parameter of plasma on the property of prohibited band gaps was analyzed.The results illustrate that the band gaps can be tuned by changing dielectric constant,thickness of dielectric layer and plasma frequency,the bandwidth of prohibited band gaps can not be broadened by increasing periodic and plasma collision frequency.The results are good theoretical references to design 1-D ternary unmagnetized plasma photonic crystal devices.
In order to study property of prohibit band gaps in 1-D ternary unmagnetized plasma photonic crystals,the transfer matrix method was applied to simulate the electromagnetic wave propagation through 1-D ternary unmagnetized plasma photonic crystals.Based on the calculated transmission coefficients,effect of periodic constant,dielectric constant,thickness of dielectric layer and parameter of plasma on the property of prohibited band gaps was analyzed.The results illustrate that the band gaps can be tuned by changing dielectric constant,thickness of dielectric layer and plasma frequency,the bandwidth of prohibited band gaps can not be broadened by increasing periodic and plasma collision frequency.The results are good theoretical references to design 1-D ternary unmagnetized plasma photonic crystal devices.
2011, 35(4): 570-572.
doi: 10.3969/j.issn.1001-3806.2011.04.032
Abstract:
In order to study the characteristics of band-gaps of 1-D biperiodic photonic crystals,the band-gaps of 1-D biperiodic photonic crystals prepared at different wavelengths were calculated by means of transfer matrix method.Calculation results show that the band-gap in this biperiodic structure is equivalent to the sum of both the single band gaps.Under certain conditions,the band gaps of the biperiodic photonic crystals were broadened.The home position of the broadened band gap is equal to the mean value of both the single positions.
In order to study the characteristics of band-gaps of 1-D biperiodic photonic crystals,the band-gaps of 1-D biperiodic photonic crystals prepared at different wavelengths were calculated by means of transfer matrix method.Calculation results show that the band-gap in this biperiodic structure is equivalent to the sum of both the single band gaps.Under certain conditions,the band gaps of the biperiodic photonic crystals were broadened.The home position of the broadened band gap is equal to the mean value of both the single positions.
2011, 35(4): 573-576.
doi: 10.3969/j.issn.1001-3806.2011.04.033
Abstract:
In order to test the edge of a target,the method of laser scanning,with which the target profile can be measured by detecting the change of return laser energy,was introduced.The random facet model was employed to establish the rough plane scattering theory,based on which the intensity distribution of the scattered laser from random rough plane surfaces can be calculated.By means of peak (valley) value detection or across-zero detection,the edge message of target can be obtained.The results prove that the proposed approach is effective on the detection of target profiles.
In order to test the edge of a target,the method of laser scanning,with which the target profile can be measured by detecting the change of return laser energy,was introduced.The random facet model was employed to establish the rough plane scattering theory,based on which the intensity distribution of the scattered laser from random rough plane surfaces can be calculated.By means of peak (valley) value detection or across-zero detection,the edge message of target can be obtained.The results prove that the proposed approach is effective on the detection of target profiles.
2011, 35(4): 535-538.
doi: 10.3969/j.issn.1001-3806.2011.04.023
Abstract:
In order to study effect of deposition conditions on morphology and deposition velocity of LiH films,LiH films were prepared on Si(100) substrate by means of pulsed laser deposition.The deposition velocity of LiH films were controlled by changing the substrate-target distance and hydrogen pressure.The relations among hydrogen pressure,deposition velocity and surface quality of the films were obtained.The results showed that the deposition velocity of LiH films decreased with hydrogen pressure and substrate-target distance increasing,moreover,the surface roughness can be reduced by increasing the hydrogen pressure to a certain degree.The relation between surface roughness and hydrogen pressure was discussed based on the growth mechanism of films.The theoretical values are in good agreement with experimental values.
In order to study effect of deposition conditions on morphology and deposition velocity of LiH films,LiH films were prepared on Si(100) substrate by means of pulsed laser deposition.The deposition velocity of LiH films were controlled by changing the substrate-target distance and hydrogen pressure.The relations among hydrogen pressure,deposition velocity and surface quality of the films were obtained.The results showed that the deposition velocity of LiH films decreased with hydrogen pressure and substrate-target distance increasing,moreover,the surface roughness can be reduced by increasing the hydrogen pressure to a certain degree.The relation between surface roughness and hydrogen pressure was discussed based on the growth mechanism of films.The theoretical values are in good agreement with experimental values.
