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RSS2016 Vol. 40, No. 3
Display Method:
2016, 40(3): 307-310.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.001
[Abstract]
[PDF 1253KB]
Abstract:
In order to achieve ultrashort laser pulse output by all fiber chirped pulse amplification technique, dispersion compensation fiber and single mode fiber were used to stretch and compress the laser pulse in the time domain, respectively. The laser system was structured by three components: oscillator, pre-amplifier and main amplifier. The whole laser system was verified theoretically and experimentally. Ultrashort pulse laser with pulse duration of 420fs and average power of 1.81W was obtained. One piece of periodically poled lithium niobate crystal was employed to yield second-harmonic generation, so that the operating wavelength was extended to near infrared region centered at 780nm with full width at half maximum of 11nm. The results show that the spectra distortion can be precisely controlled during the whole amplification process by adjusting the insert dispersion. The study could be very helpful for study on high power all fiber ultrashort fiber amplifiers.
In order to achieve ultrashort laser pulse output by all fiber chirped pulse amplification technique, dispersion compensation fiber and single mode fiber were used to stretch and compress the laser pulse in the time domain, respectively. The laser system was structured by three components: oscillator, pre-amplifier and main amplifier. The whole laser system was verified theoretically and experimentally. Ultrashort pulse laser with pulse duration of 420fs and average power of 1.81W was obtained. One piece of periodically poled lithium niobate crystal was employed to yield second-harmonic generation, so that the operating wavelength was extended to near infrared region centered at 780nm with full width at half maximum of 11nm. The results show that the spectra distortion can be precisely controlled during the whole amplification process by adjusting the insert dispersion. The study could be very helpful for study on high power all fiber ultrashort fiber amplifiers.
2016, 40(3): 311-314.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.002
Abstract:
In order to get high energy long pulse and high peak power short pulse in one laser at the same time, coaxial superimposed pulse laser output with two characteristics was obtained in a single laser by using different gain areas of the same working material. The results show that by using potassium titanyl phosphate electro-optical Q-switch with high resistivity, the superimposed pulse with long pulsewidth of 10ms and short pulsewidth of 63ns is gotten in bi-xenon lamp pumped pulse Nd:YAG laser (cavity length of 840mm, double flat-flat cavity structure and working material length of 150mm). With pump frequency of 9Hz, peak power of 46.7kW, mean power of 93.4W and envelope energy of superimposed pulse of 10.4J were obtained. The experiment results show that the superimposed pulse laser output can reach the demands of laser drilling.
In order to get high energy long pulse and high peak power short pulse in one laser at the same time, coaxial superimposed pulse laser output with two characteristics was obtained in a single laser by using different gain areas of the same working material. The results show that by using potassium titanyl phosphate electro-optical Q-switch with high resistivity, the superimposed pulse with long pulsewidth of 10ms and short pulsewidth of 63ns is gotten in bi-xenon lamp pumped pulse Nd:YAG laser (cavity length of 840mm, double flat-flat cavity structure and working material length of 150mm). With pump frequency of 9Hz, peak power of 46.7kW, mean power of 93.4W and envelope energy of superimposed pulse of 10.4J were obtained. The experiment results show that the superimposed pulse laser output can reach the demands of laser drilling.
2016, 40(3): 315-319.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.003
Abstract:
In order to realize precise synchronization detection of signal phase for 2-D heterodyne interference displacement measurement, based on the combination of the whole cycle counting and the pulse stuffing methods, a dual-channel synchronous heterodyne signal phase measurement system based on field programmable gate array was designed and implemented by utilizing the same clock reference to detect synchronously and process the dual-channel signals parallelly. The results demonstrate that the resolution of 0.18 is realized with carrier frequency of 100kHz, and the phase synchronization measurement error of 0.18 is achieved for dual-channel signal detection. Accurate measurement of integral and fractional phases was realized by the system. Meanwhile, the real-time synchronous measurement of dual-channel signal phase was then guaranteed. It indicates that the developed system can fulfill the requirement of various 2-D heterodyne interference displacement measurement applications.
In order to realize precise synchronization detection of signal phase for 2-D heterodyne interference displacement measurement, based on the combination of the whole cycle counting and the pulse stuffing methods, a dual-channel synchronous heterodyne signal phase measurement system based on field programmable gate array was designed and implemented by utilizing the same clock reference to detect synchronously and process the dual-channel signals parallelly. The results demonstrate that the resolution of 0.18 is realized with carrier frequency of 100kHz, and the phase synchronization measurement error of 0.18 is achieved for dual-channel signal detection. Accurate measurement of integral and fractional phases was realized by the system. Meanwhile, the real-time synchronous measurement of dual-channel signal phase was then guaranteed. It indicates that the developed system can fulfill the requirement of various 2-D heterodyne interference displacement measurement applications.
2016, 40(3): 320-325.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.004
Abstract:
In order to achieve high matching precision, good real-time performance and availability of target recognizing under shade condition in laser imaging guidance, a laser image matching algorithm was proposed based on improved Hausdorff distance and quantum genetic algorithm. In terms of the traditional Hausdorff algorithm and the problems of improving Hausdorff distance, the local edge feature of the image was selected as feature space. A new algorithm of improving Hausdorff distance was proposed to use it as a similarity measure. In the search strategy, the quantum genetic algorithm was chosen for parallel search. In order to prevent premature convergence of the population, the population catastrophe strategy was proposed and the speed and direction of convergence were adjusted by applying dynamic quantum rotation. Through theoretical analysis and experimental verification, target recognition contrast data under the condition of different parameters was obtained. The results show that the new algorithm, with good robustness, high matching precision and fast computing speed, could eliminate the effect of partial occlusion, noise and outlier.
In order to achieve high matching precision, good real-time performance and availability of target recognizing under shade condition in laser imaging guidance, a laser image matching algorithm was proposed based on improved Hausdorff distance and quantum genetic algorithm. In terms of the traditional Hausdorff algorithm and the problems of improving Hausdorff distance, the local edge feature of the image was selected as feature space. A new algorithm of improving Hausdorff distance was proposed to use it as a similarity measure. In the search strategy, the quantum genetic algorithm was chosen for parallel search. In order to prevent premature convergence of the population, the population catastrophe strategy was proposed and the speed and direction of convergence were adjusted by applying dynamic quantum rotation. Through theoretical analysis and experimental verification, target recognition contrast data under the condition of different parameters was obtained. The results show that the new algorithm, with good robustness, high matching precision and fast computing speed, could eliminate the effect of partial occlusion, noise and outlier.
2016, 40(3): 326-330.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.005
Abstract:
In order to study nonlinear refractive index of bismuth telluride, a 3-D topological insulator, nonlinear refractive index of 800nm femtosecond pulse laser was measured by reflection z-scan method. After theoretical calculation and experimental data fitting, nonlinear refractive index of bismuth telluride crystal could reach the order of magnitude of 10-14m2/W, 105 times of that of quartz. Nonlinear refractive index decreased with the increase of incident power. Until peak intensity reached 85GW/cm2, nonlinear refractive index tended to be a constant. The results show that bismuth telluride is a remarkable nonlinear optical material which has huge potential in the application of all-optical signal processing and optical switching.
In order to study nonlinear refractive index of bismuth telluride, a 3-D topological insulator, nonlinear refractive index of 800nm femtosecond pulse laser was measured by reflection z-scan method. After theoretical calculation and experimental data fitting, nonlinear refractive index of bismuth telluride crystal could reach the order of magnitude of 10-14m2/W, 105 times of that of quartz. Nonlinear refractive index decreased with the increase of incident power. Until peak intensity reached 85GW/cm2, nonlinear refractive index tended to be a constant. The results show that bismuth telluride is a remarkable nonlinear optical material which has huge potential in the application of all-optical signal processing and optical switching.
2016, 40(3): 331-334.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.006
Abstract:
In order to solve the missing projectile under high-speed photography which caused by short time, harder synchrotron and low-light-level, a synchronous trigger light source system was designed. A high brightness light-emitting didoe(LED) array controlled by the field-programmable gate array was used as light source. The simulation of LED array by MATLAB software shows that the maximum intensity of the light source array can reach 9104 Lux one meter away from the center position of light source. In the experiment, the camera is triggered when the projectile leaves the muzzle. At the same time, the camera outputs a synchronous trigger signal to trigger the lighting system. The results show that, the bullet charge is 0.15g and the camera frame rate is 5000frame/s. Collide speed is about 100m/s. Experiment results demonstrate that the synchronous trigger system has an effective improvement of the illumination intensity and the degree of synchronization. This study is helpful to improve the projectile testing technology.
In order to solve the missing projectile under high-speed photography which caused by short time, harder synchrotron and low-light-level, a synchronous trigger light source system was designed. A high brightness light-emitting didoe(LED) array controlled by the field-programmable gate array was used as light source. The simulation of LED array by MATLAB software shows that the maximum intensity of the light source array can reach 9104 Lux one meter away from the center position of light source. In the experiment, the camera is triggered when the projectile leaves the muzzle. At the same time, the camera outputs a synchronous trigger signal to trigger the lighting system. The results show that, the bullet charge is 0.15g and the camera frame rate is 5000frame/s. Collide speed is about 100m/s. Experiment results demonstrate that the synchronous trigger system has an effective improvement of the illumination intensity and the degree of synchronization. This study is helpful to improve the projectile testing technology.
2016, 40(3): 335-338.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.007
Abstract:
In order to solve the problem of target strengh weakness of traditional target detection method based on singular value decomposition (SVD), an improved SVD algorithm was proposed for background suppression in dim and small infrared target detection. According to the nature of SVD, nonlinear transformation was adopted to improve the middle order part of image singular values for the largest contribution to the goal. And then, the other singular value was set to zero,finally the target image was obtained by reconstructing image. The experimental results show that the proposed method could preserve and enhance the target signal, improve the signal-to-clutter ratio and contrast ratio,and have good performance in complicated background suppression.
In order to solve the problem of target strengh weakness of traditional target detection method based on singular value decomposition (SVD), an improved SVD algorithm was proposed for background suppression in dim and small infrared target detection. According to the nature of SVD, nonlinear transformation was adopted to improve the middle order part of image singular values for the largest contribution to the goal. And then, the other singular value was set to zero,finally the target image was obtained by reconstructing image. The experimental results show that the proposed method could preserve and enhance the target signal, improve the signal-to-clutter ratio and contrast ratio,and have good performance in complicated background suppression.
2016, 40(3): 339-343.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.008
Abstract:
In order to evaluate the performance of plane holographic grating exposure system and study the influence of interference fringe's phase changes on grating manufacture, based on exposure dose expression and binary model of grating mask profile, the effect of fringe's phase vibration on exposure contrast, grating mask profile and exposure phase were analyzed by theoretical analysis and numerical calculation. The results show that all kinds of interference fringe low-frequency drift decrease exposure contrast and the controllability of grating mask profile is reduced. The influence has consistency. For keeping the exposure contrast greater than 0.95, root mean square(RMS) value of low-frequency drift needs to be controlled in the range of 0.05 fringe's period. The effect of small amplitude high frequency vibration on grating exposure can be neglected. Exposure phase error caused by low-frequency shift doesn't impact diffractive characteristic of grating. For getting qualified grating mask, the matching relationship between photoresist nonlinearity and exposure should be controlled and RMS of low frequency drift should be smaller than 1/20 fringe's period which can be used to evaluate the stability of holographic grating exposure system.
In order to evaluate the performance of plane holographic grating exposure system and study the influence of interference fringe's phase changes on grating manufacture, based on exposure dose expression and binary model of grating mask profile, the effect of fringe's phase vibration on exposure contrast, grating mask profile and exposure phase were analyzed by theoretical analysis and numerical calculation. The results show that all kinds of interference fringe low-frequency drift decrease exposure contrast and the controllability of grating mask profile is reduced. The influence has consistency. For keeping the exposure contrast greater than 0.95, root mean square(RMS) value of low-frequency drift needs to be controlled in the range of 0.05 fringe's period. The effect of small amplitude high frequency vibration on grating exposure can be neglected. Exposure phase error caused by low-frequency shift doesn't impact diffractive characteristic of grating. For getting qualified grating mask, the matching relationship between photoresist nonlinearity and exposure should be controlled and RMS of low frequency drift should be smaller than 1/20 fringe's period which can be used to evaluate the stability of holographic grating exposure system.
2016, 40(3): 344-348.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.009
Abstract:
Image method was often used to measure the slumping angles. However, the method has a problem that measurement standard deviation is large (about 0.5). In order to resolve the problems, online measurement method of dynamic speckle contrast slumping angle was proposed. When laser irradiated on the granules in rotating drum, dynamic speckle formed in far field. Linear CCD camera was used to get the speckle image with the changing of time. Through the analysis of the contrast of speckle images, the speed fluctuation of granular flows was calculated and interval time between two slumping angles was found. Finally slumping angles can be calculated out by using speed multiplied by interval time. Glass beads with diameter distribution of 1mm~1.25mm were used. Dynamic speckle contrast method and image method were used respectively to measure the slumping angles under different rotational speeds. The results show that online measurement of dynamic speckle contrast slumping angle is high spatial and temporal resolution. The standard deviation of measurement data is small, repeatability is better and the determination of data fitting coefficient is high. Dynamic speckle contrast method is applicable for online measurement and scientific research of granular flow in rotating drums.
Image method was often used to measure the slumping angles. However, the method has a problem that measurement standard deviation is large (about 0.5). In order to resolve the problems, online measurement method of dynamic speckle contrast slumping angle was proposed. When laser irradiated on the granules in rotating drum, dynamic speckle formed in far field. Linear CCD camera was used to get the speckle image with the changing of time. Through the analysis of the contrast of speckle images, the speed fluctuation of granular flows was calculated and interval time between two slumping angles was found. Finally slumping angles can be calculated out by using speed multiplied by interval time. Glass beads with diameter distribution of 1mm~1.25mm were used. Dynamic speckle contrast method and image method were used respectively to measure the slumping angles under different rotational speeds. The results show that online measurement of dynamic speckle contrast slumping angle is high spatial and temporal resolution. The standard deviation of measurement data is small, repeatability is better and the determination of data fitting coefficient is high. Dynamic speckle contrast method is applicable for online measurement and scientific research of granular flow in rotating drums.
2016, 40(3): 349-352.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.010
Abstract:
In order to realize 1120nm ytterbium-doped fiber laser with narrow linewidth, high power level, long wavelength (compared with 1030nm~1080nm), the resonator of fiber laser was composed of a normal single-mode Yb-doped fiber and a pair of fiber Bragg gratings (FBG). The theoretical-optimized active fiber length is used to ensure that pump light is entirely absorbed and nonlinear effect is suppressed. After theoretical analysis and experimental verification, the results show that when laser threshold pump power is 40mW and the launched pump power is 265mW, laser output signal power is up to 35mW with optical-to-optical conversion efficiency of 13.2%, central wavelength of 1120.9nm, output light linewidth of 0.03nm. The performances of the laser contribute to high reflectivity output coupler FBG, short cavity and low power operation. The laser can be injected into fiber amplifiers.
In order to realize 1120nm ytterbium-doped fiber laser with narrow linewidth, high power level, long wavelength (compared with 1030nm~1080nm), the resonator of fiber laser was composed of a normal single-mode Yb-doped fiber and a pair of fiber Bragg gratings (FBG). The theoretical-optimized active fiber length is used to ensure that pump light is entirely absorbed and nonlinear effect is suppressed. After theoretical analysis and experimental verification, the results show that when laser threshold pump power is 40mW and the launched pump power is 265mW, laser output signal power is up to 35mW with optical-to-optical conversion efficiency of 13.2%, central wavelength of 1120.9nm, output light linewidth of 0.03nm. The performances of the laser contribute to high reflectivity output coupler FBG, short cavity and low power operation. The laser can be injected into fiber amplifiers.
2016, 40(3): 353-357.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.011
Abstract:
In order to optimize welding parameters of laser-heated friction stir welding (FSW) and provide theoretical foundation for experiments, numerical simulation was adopted and simulation of 3-D flow field of Q235 steel laser-assisted heating FSW was conducted. Flow behavior and heat transfer process ofviscoplastic material were analyzed. Flow field and temperature distribution of welding material were acquired.The results show that the welding material is transported mainly along the retreating side.When rotational speed increases from 750r/min to 1180r/min under the condition of 800W laser power and 23.5mm/min welding speed, the material flow gets stronger. The highest temperature rises, but not more than the melting point of steel. The phenomenon is consistent with that the steel does not melt in the process of the actual experiment. Laser, as an auxiliary heat source,can provide heat input during the welding process and can improve mobility of welding materials.
In order to optimize welding parameters of laser-heated friction stir welding (FSW) and provide theoretical foundation for experiments, numerical simulation was adopted and simulation of 3-D flow field of Q235 steel laser-assisted heating FSW was conducted. Flow behavior and heat transfer process ofviscoplastic material were analyzed. Flow field and temperature distribution of welding material were acquired.The results show that the welding material is transported mainly along the retreating side.When rotational speed increases from 750r/min to 1180r/min under the condition of 800W laser power and 23.5mm/min welding speed, the material flow gets stronger. The highest temperature rises, but not more than the melting point of steel. The phenomenon is consistent with that the steel does not melt in the process of the actual experiment. Laser, as an auxiliary heat source,can provide heat input during the welding process and can improve mobility of welding materials.
2016, 40(3): 358-362.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.012
Abstract:
In order to solve the problem of being sensitive to temperature for output light of a quartz optical filter, based on the principle that the value of quartz birefringence and quartz rotation had opposite trend with the change of temperature, a new temperature insensitive quartz filter was presented combining a quartz birefringent filter with a quartz rotation filter. By numerical analysis and experimental methods, the impact of temperature on output center wavelength of the new type quartz filter was studied. The results show that new quartz filter is insensitive to temperature in a certain range. The new quartz filter provides adaptive temperature compensation for the insensitive temperature quartz filter.
In order to solve the problem of being sensitive to temperature for output light of a quartz optical filter, based on the principle that the value of quartz birefringence and quartz rotation had opposite trend with the change of temperature, a new temperature insensitive quartz filter was presented combining a quartz birefringent filter with a quartz rotation filter. By numerical analysis and experimental methods, the impact of temperature on output center wavelength of the new type quartz filter was studied. The results show that new quartz filter is insensitive to temperature in a certain range. The new quartz filter provides adaptive temperature compensation for the insensitive temperature quartz filter.
2016, 40(3): 363-366.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.013
Abstract:
In order to study effect of pulse width of pump light on Brillouin scattering light, three-wave coupling equations of stimulated Brillouin scattering in optical fiber sensing system were researched. The approximate expressions of scattering light were deduced based on frequency domain analysis and perturbation approximation theory. The influence of pulse width on Brillouin spectrum was analyzed through numerical calculation. The results show that a multi-peak structure of Brillouin scattering spectrum is gotten when the width is close to 20ns(phonon lifetime). When the width is more and more close to 40ns, the main peak increases and the sub-peak decreases gradually. When pulse width is far greater than phonon lifetime, scattering spectrum appears only one peak and maintains a constant peak. The study gives references for the choose of suitable pulse width in sensing.
In order to study effect of pulse width of pump light on Brillouin scattering light, three-wave coupling equations of stimulated Brillouin scattering in optical fiber sensing system were researched. The approximate expressions of scattering light were deduced based on frequency domain analysis and perturbation approximation theory. The influence of pulse width on Brillouin spectrum was analyzed through numerical calculation. The results show that a multi-peak structure of Brillouin scattering spectrum is gotten when the width is close to 20ns(phonon lifetime). When the width is more and more close to 40ns, the main peak increases and the sub-peak decreases gradually. When pulse width is far greater than phonon lifetime, scattering spectrum appears only one peak and maintains a constant peak. The study gives references for the choose of suitable pulse width in sensing.
2016, 40(3): 367-371.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.014
Abstract:
In order to evaluate optical characteristics of auto-stereoscopic display, taking 8 viewpoint parallax barrier auto-stereoscopic display as an example, optical characteristics of auto-stereoscopic display of different viewpoint images were studied and the values of brightness and chromaticity at different visual angles were measured. Optical characteristics included optimal viewing position, crosstalk, viewing range, brightness uniformity, chromaticity uniformity and Moir fringes. The obtained data samples were analyzed. The results show that the method of measurement and analysis can evaluate the optical characteristics of multi-viewpoint stereoscopic display quantitatively and enhance the objectivity about the performance assessment of stereoscopic display. The study has an instructive effect on auto-stereoscopic display design.
In order to evaluate optical characteristics of auto-stereoscopic display, taking 8 viewpoint parallax barrier auto-stereoscopic display as an example, optical characteristics of auto-stereoscopic display of different viewpoint images were studied and the values of brightness and chromaticity at different visual angles were measured. Optical characteristics included optimal viewing position, crosstalk, viewing range, brightness uniformity, chromaticity uniformity and Moir fringes. The obtained data samples were analyzed. The results show that the method of measurement and analysis can evaluate the optical characteristics of multi-viewpoint stereoscopic display quantitatively and enhance the objectivity about the performance assessment of stereoscopic display. The study has an instructive effect on auto-stereoscopic display design.
2016, 40(3): 372-376.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.015
Abstract:
In order to explore the absorption features of rat brain tissue at different ischemia time, the model of middle cerebral artery occlusion was established and terahertz time-domain spectroscopy of ischemic rat brain tissue was measured. After theoretical analysis and experimental evaluation, terahertz absorption coefficient of ischemic brain tissue at different time in the frequency band from 0.4THz to 0.95THz was acquired. The results show that different absorption characteristics to terahertz wave at different time of ischemic brain tissue is due to intermediates, such as excitatory amino acids produced by ischemia brain injury cascade, lactic acid produced by anaerobic respiration, and large quantities of nitric oxide synthesis produced by calcium overload. The results will have an important role in studying the pathology mechanisms of ischemic brain injury and have a certain value in the biomedical field.
In order to explore the absorption features of rat brain tissue at different ischemia time, the model of middle cerebral artery occlusion was established and terahertz time-domain spectroscopy of ischemic rat brain tissue was measured. After theoretical analysis and experimental evaluation, terahertz absorption coefficient of ischemic brain tissue at different time in the frequency band from 0.4THz to 0.95THz was acquired. The results show that different absorption characteristics to terahertz wave at different time of ischemic brain tissue is due to intermediates, such as excitatory amino acids produced by ischemia brain injury cascade, lactic acid produced by anaerobic respiration, and large quantities of nitric oxide synthesis produced by calcium overload. The results will have an important role in studying the pathology mechanisms of ischemic brain injury and have a certain value in the biomedical field.
2016, 40(3): 377-382.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.016
Abstract:
In order to improve location and width measurement precision of optical surface scratches, a sub-pixel edge detection algorithm based on discrete orthogonal polynomial surface fitting was proposed. Sub-pixel edge detection was realized by fitting the edge points and their neighborhood into surfaces instead of by curve fitting only in the gradient direction of the edge points. By using the acceleration strategy of the region of interest and the method of fast solving surface equation parameters based on discrete orthogonal polynomial, the processing time was greatly reduced. In terms of width calculation, the Euclidean distance of each section was calculated after the scratch was divided into a series of small segments adaptively and then the maximum width was the width of scratch. The experimental results show that the proposed method has high accuracy and strong robustness. Mean error of width is less than 5.2% and standard deviation of width is less than 0.3 of the same scratches measured under different visual windows by this algorithm. In terms of processing time to solve the surface model parameter, the processing time of acceleration strategy is 7.35% of the least square method and is greatly reduced. This method can meet the requirements of fast and high precision measurement in engineering application.
In order to improve location and width measurement precision of optical surface scratches, a sub-pixel edge detection algorithm based on discrete orthogonal polynomial surface fitting was proposed. Sub-pixel edge detection was realized by fitting the edge points and their neighborhood into surfaces instead of by curve fitting only in the gradient direction of the edge points. By using the acceleration strategy of the region of interest and the method of fast solving surface equation parameters based on discrete orthogonal polynomial, the processing time was greatly reduced. In terms of width calculation, the Euclidean distance of each section was calculated after the scratch was divided into a series of small segments adaptively and then the maximum width was the width of scratch. The experimental results show that the proposed method has high accuracy and strong robustness. Mean error of width is less than 5.2% and standard deviation of width is less than 0.3 of the same scratches measured under different visual windows by this algorithm. In terms of processing time to solve the surface model parameter, the processing time of acceleration strategy is 7.35% of the least square method and is greatly reduced. This method can meet the requirements of fast and high precision measurement in engineering application.
2016, 40(3): 383-387.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.017
Abstract:
The advantages to poly silicon film instead of amorphous silicon film in the field of flat panel display were introduced. Crystallization process of poly silicon film by using excimer laser crystallization system was studied. The principle of how lens array achieve the uniformity of output laser energy density was described. The structure of typical excimer laser annealing(ELA) line beam shaping system, which included beam expanding unit, beam energy homogenizing unit, projection unit and so on was focused on. Finally the application of sequential lateral solidification technology in the area of low temperature poly silicon(LTPS) using excimer laser nnealing was introduced. The status of ELA optical system was discussed and its significance in flat panel display industry was pointed out.
The advantages to poly silicon film instead of amorphous silicon film in the field of flat panel display were introduced. Crystallization process of poly silicon film by using excimer laser crystallization system was studied. The principle of how lens array achieve the uniformity of output laser energy density was described. The structure of typical excimer laser annealing(ELA) line beam shaping system, which included beam expanding unit, beam energy homogenizing unit, projection unit and so on was focused on. Finally the application of sequential lateral solidification technology in the area of low temperature poly silicon(LTPS) using excimer laser nnealing was introduced. The status of ELA optical system was discussed and its significance in flat panel display industry was pointed out.
2016, 40(3): 388-391.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.018
Abstract:
In order to study the relationship between tilted angles of parallax barriers and crosstalk quantitatively and seek for the best tilted angle, a simulation model for crosstalk and tilted angles was established based on the optical path equation. Meanwhile crosstalk in front of the screen was simulated in vertical and horizontal directions respectively. The results show that the viewing zone in horizontal direction decreases linearly, however the viewing zone in vertical direction is not in the same case but decreases step by step. Theoretical explanation of the phenomenon was put forward and the quantitative relationship between tilted angle of parallax barrier and crosstalk was obtained. The study would provide a significant guidance for auto-stereoscpoic display based on slanted parallax barrier.
In order to study the relationship between tilted angles of parallax barriers and crosstalk quantitatively and seek for the best tilted angle, a simulation model for crosstalk and tilted angles was established based on the optical path equation. Meanwhile crosstalk in front of the screen was simulated in vertical and horizontal directions respectively. The results show that the viewing zone in horizontal direction decreases linearly, however the viewing zone in vertical direction is not in the same case but decreases step by step. Theoretical explanation of the phenomenon was put forward and the quantitative relationship between tilted angle of parallax barrier and crosstalk was obtained. The study would provide a significant guidance for auto-stereoscpoic display based on slanted parallax barrier.
2016, 40(3): 392-396.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.019
Abstract:
In order to measure 3-D profile of a sample with high accuracy, wavenumber-scanning interferometry was used. An optical wedge was used as reference terminal of a Michelson interferometer system. The phases of wedge interference image were extracted by 2-D Fourier transform. The changes of output wavenumber were detected on line. Finally, all the time-resolved interferometry image sequences were sampled by Fourier transform random. The 3-D contour of object surface was restored with high precision. The profile of a sample object was constructed with the resolution of 6.7nm. The proposed method is particularly suitable for quality inspection of mechanical parts.
In order to measure 3-D profile of a sample with high accuracy, wavenumber-scanning interferometry was used. An optical wedge was used as reference terminal of a Michelson interferometer system. The phases of wedge interference image were extracted by 2-D Fourier transform. The changes of output wavenumber were detected on line. Finally, all the time-resolved interferometry image sequences were sampled by Fourier transform random. The 3-D contour of object surface was restored with high precision. The profile of a sample object was constructed with the resolution of 6.7nm. The proposed method is particularly suitable for quality inspection of mechanical parts.
2016, 40(3): 397-400.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.020
Abstract:
Photodynamic therapy instrument is one of the new types of cancer treatment instruments by using photodynamic therapy. In order to solve the color purity problem of photodynamic irradiation treatment, photonic crystal theory was applied and transfer matrix method was used. The bandgap properties of photonic crystals were analyzed by MATLAB programming to select appropriate photonic crystal materials and to determine its structural parameters. The results show that, newly designed photonic crystal structure has good filtering characteristic, which allows only the pass-through of 980nm near infrared light, and has therapeutic effect on liver cancer, gastric cancer and other visceral organ cancers. Photonic crystal filters based on such structure can be applied to ordinary photodynamic therapy instruments and play the greater role in cancer treatment.
Photodynamic therapy instrument is one of the new types of cancer treatment instruments by using photodynamic therapy. In order to solve the color purity problem of photodynamic irradiation treatment, photonic crystal theory was applied and transfer matrix method was used. The bandgap properties of photonic crystals were analyzed by MATLAB programming to select appropriate photonic crystal materials and to determine its structural parameters. The results show that, newly designed photonic crystal structure has good filtering characteristic, which allows only the pass-through of 980nm near infrared light, and has therapeutic effect on liver cancer, gastric cancer and other visceral organ cancers. Photonic crystal filters based on such structure can be applied to ordinary photodynamic therapy instruments and play the greater role in cancer treatment.
2016, 40(3): 401-404.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.021
Abstract:
By using fluorescence spectroscopy measurement method and ORIGIN software, new type of aggregation induced emission(AIE) material (1-rhodanine-pyrene) was studied by theoretical analysis and experimental verification and some new optical properties were discovered. The results show that when the concentration of solution dilutes, the emission peak of the sample shows a sharp blue shift. When the temperature increases, fluorescence strength of the sample enhances. These properties are different from common AIE materials, and it is related to super molecular structure induced from 1-rhodanine-pyrene aggregation in solution. The material has certain application prospect in biological imaging, medical field, sensors, photoelectric detection and organic display. The study has important significance in organic light-emitting materials.
By using fluorescence spectroscopy measurement method and ORIGIN software, new type of aggregation induced emission(AIE) material (1-rhodanine-pyrene) was studied by theoretical analysis and experimental verification and some new optical properties were discovered. The results show that when the concentration of solution dilutes, the emission peak of the sample shows a sharp blue shift. When the temperature increases, fluorescence strength of the sample enhances. These properties are different from common AIE materials, and it is related to super molecular structure induced from 1-rhodanine-pyrene aggregation in solution. The material has certain application prospect in biological imaging, medical field, sensors, photoelectric detection and organic display. The study has important significance in organic light-emitting materials.
2016, 40(3): 405-408.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.022
Abstract:
In order to use fractional-order Fourier transform(FRFT) to effectively detect coefficient of chirp signal,characterization of linear chirped ultrashort pulse was studied based on FRFT. FRFT has characteristics of high energy aggregation in an optimal order. According to the characterization, the relationship between optimal order and chirped coefficient of ultrashort pulse was proved theoretically. Numerical simulation was done for Gaussian linear-chirped pulse. The relationship curve between the fractional order and the maximum of the result of FRFT was drawn. The results show that the theoretical formula is in agreement with numerical simulation. The conclusion can provide reference for discussing chirp coefficient of ultrashort pulse.
In order to use fractional-order Fourier transform(FRFT) to effectively detect coefficient of chirp signal,characterization of linear chirped ultrashort pulse was studied based on FRFT. FRFT has characteristics of high energy aggregation in an optimal order. According to the characterization, the relationship between optimal order and chirped coefficient of ultrashort pulse was proved theoretically. Numerical simulation was done for Gaussian linear-chirped pulse. The relationship curve between the fractional order and the maximum of the result of FRFT was drawn. The results show that the theoretical formula is in agreement with numerical simulation. The conclusion can provide reference for discussing chirp coefficient of ultrashort pulse.
2016, 40(3): 409-412.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.023
Abstract:
In order to achieve high conversion rate of 3m infrared laser output from an optical parametric oscillation, by using the applied pulse electric field method, periodically poled grating of 31.2m was prepared on MgO-doped(mole fraction of 0.05) lithium niobate crystal with the thickness of 1mm. The relationship between idler wavelength and temperature when periodically poled MgO-doped LiNbO3 pumped by 1064nm pulsed laser was studied by theoretical calculation and simulation. Acousto-optic Q-switched Nd:YAG laser with the wavelength of 1064nm was used as the fundamental source to operate optical parametric oscillation experiment with pulse width of 200ns and repetition rate of 20kHz. When pulse input power is 5.567W at the temperature of 80℃, idler output power of 1.141W was obtained with output wavelength of 3m. The maximum conversion efficiency from incident pump power to idler output was 20.1%. The results show that this method of preparation by periodically poled lithium niobate optical parametric oscillation has high optical conversion efficiency.
In order to achieve high conversion rate of 3m infrared laser output from an optical parametric oscillation, by using the applied pulse electric field method, periodically poled grating of 31.2m was prepared on MgO-doped(mole fraction of 0.05) lithium niobate crystal with the thickness of 1mm. The relationship between idler wavelength and temperature when periodically poled MgO-doped LiNbO3 pumped by 1064nm pulsed laser was studied by theoretical calculation and simulation. Acousto-optic Q-switched Nd:YAG laser with the wavelength of 1064nm was used as the fundamental source to operate optical parametric oscillation experiment with pulse width of 200ns and repetition rate of 20kHz. When pulse input power is 5.567W at the temperature of 80℃, idler output power of 1.141W was obtained with output wavelength of 3m. The maximum conversion efficiency from incident pump power to idler output was 20.1%. The results show that this method of preparation by periodically poled lithium niobate optical parametric oscillation has high optical conversion efficiency.
2016, 40(3): 413-416.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.024
Abstract:
In order to study the effect of hot wire temperature on the properties of a-SiNx:H thin films, by using hot wire chemical vapor deposition method and using SiH4, NH3, H2 as reaction gas source, a-SiNx:H films were deposited by changing the temperature of hot wire. Film luminescent properties, microstructure and bonding characteristics were gotten and analyzed in detail by means of measurement methods such as ultraviolet-visible optical absorption spectroscopy, Fourier transform infrared transmission spectroscopy, and photoluminescence spectrum. The results show that, when wire temperature is at 1645℃, H content reaches greatest, N content is extremely small, film has high refractive index and a large degree of order. When the wire temperature is at 1713℃, H content decreases, N content reaches extremes. And then, with the increase of hot wire temperature, N content decreases and internal defect intensity increases. The results show that the best value of hot filament temperature is between 1596℃ to 1680℃ and the refractive index of film is 2.0. The film, with full nitrogen and hydrogen contents and stable structure and characteristics, is suit to choose as silicon-based solar cell antireflection film.
In order to study the effect of hot wire temperature on the properties of a-SiNx:H thin films, by using hot wire chemical vapor deposition method and using SiH4, NH3, H2 as reaction gas source, a-SiNx:H films were deposited by changing the temperature of hot wire. Film luminescent properties, microstructure and bonding characteristics were gotten and analyzed in detail by means of measurement methods such as ultraviolet-visible optical absorption spectroscopy, Fourier transform infrared transmission spectroscopy, and photoluminescence spectrum. The results show that, when wire temperature is at 1645℃, H content reaches greatest, N content is extremely small, film has high refractive index and a large degree of order. When the wire temperature is at 1713℃, H content decreases, N content reaches extremes. And then, with the increase of hot wire temperature, N content decreases and internal defect intensity increases. The results show that the best value of hot filament temperature is between 1596℃ to 1680℃ and the refractive index of film is 2.0. The film, with full nitrogen and hydrogen contents and stable structure and characteristics, is suit to choose as silicon-based solar cell antireflection film.
2016, 40(3): 417-421.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.025
Abstract:
In order to explore effect of laser cutting on fatigue performance of aircraft fuselage skin, by using the method of simulation and contrast test method respectively, fatigue performance of aircraft skin material was studied by theoretical analysis and experimental verification. Analysis data of finite element fatigue of aircraft skin material, and comparison data of fatigue performance test of laser cutting specimen and mechanical milling specimen were obtained. At the same time, fatigue fracture of aircraft skin plate was scanned and analyzed by scanning electron microscope. The analysis results show that after laser cutting, fatigue life of aircraft skin material is about 5.4104. After mechanical milling, fatigue life is 2.34105. Laser cutting has a certain impact on fatigue performance of aircraft fuselage skin materials, but its fatigue life can increase through grinding and processing of cutting seams.
In order to explore effect of laser cutting on fatigue performance of aircraft fuselage skin, by using the method of simulation and contrast test method respectively, fatigue performance of aircraft skin material was studied by theoretical analysis and experimental verification. Analysis data of finite element fatigue of aircraft skin material, and comparison data of fatigue performance test of laser cutting specimen and mechanical milling specimen were obtained. At the same time, fatigue fracture of aircraft skin plate was scanned and analyzed by scanning electron microscope. The analysis results show that after laser cutting, fatigue life of aircraft skin material is about 5.4104. After mechanical milling, fatigue life is 2.34105. Laser cutting has a certain impact on fatigue performance of aircraft fuselage skin materials, but its fatigue life can increase through grinding and processing of cutting seams.
2016, 40(3): 422-425.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.026
Abstract:
Laser scanning and perforating systems have advantages of simple and reliable controlling structure, high perforation efficiency and good quality. Perforation systems have been widely used to perforate thin material such as paper, leather and plaster to improve the permeability and discourage the counterfeit. In order to solve the problem of expensive cost and low efficiency of the existing laser perforating equipment, an online plaster perforation system was proposed based on continuous wave CO2 laser, embedded control system and galvanometer scanning. The experiment results show that the system can adjust hole diameter from 0.2mm to 1.2mm and space between holes in the range of 4mm~10mm at online speed of 2m/min~12m/min. This experiment is useful to improve the efficiency of plaster laser perforation processing and expand the market of laser drilling equipment.
Laser scanning and perforating systems have advantages of simple and reliable controlling structure, high perforation efficiency and good quality. Perforation systems have been widely used to perforate thin material such as paper, leather and plaster to improve the permeability and discourage the counterfeit. In order to solve the problem of expensive cost and low efficiency of the existing laser perforating equipment, an online plaster perforation system was proposed based on continuous wave CO2 laser, embedded control system and galvanometer scanning. The experiment results show that the system can adjust hole diameter from 0.2mm to 1.2mm and space between holes in the range of 4mm~10mm at online speed of 2m/min~12m/min. This experiment is useful to improve the efficiency of plaster laser perforation processing and expand the market of laser drilling equipment.
2016, 40(3): 426-431.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.027
Abstract:
In order to solve the problem of ethylene detection of trace concentration in biomedical, petrochemical industry, CO2 laser was used to excite photoacoustic spectroscopy effect in photoacoustic cell for ethylene concentration detection. Parameters of photoacoustic cell was designed and optimized. The relationship between laser lines 10P(16), 10P(18) and ethylene absorption coefficient was investigated, and the link of ethylene concentration and photoacoustic signal was studied. Through theoretical analysis and experimental research, the results show that parameters of photoacoustic system are: center of resonant frequency of 833Hz, quality factor of 20.8, and photoacoustic cell of 2323Pacm/W. When laser power is 3.6W, photoacoustic signal and ethylene volume fraction get good linear relationship under the irradiation of two laser spectrum. Linear fit is 0.99744 and 0.99802 respectively. The minimum detectable concentration of system is 0.9nmol/L. Experimental results and theoretical analysis verify the effect of photoacoustic spectroscopy detection of trace concentrations of ethylene has good appliciation value.
In order to solve the problem of ethylene detection of trace concentration in biomedical, petrochemical industry, CO2 laser was used to excite photoacoustic spectroscopy effect in photoacoustic cell for ethylene concentration detection. Parameters of photoacoustic cell was designed and optimized. The relationship between laser lines 10P(16), 10P(18) and ethylene absorption coefficient was investigated, and the link of ethylene concentration and photoacoustic signal was studied. Through theoretical analysis and experimental research, the results show that parameters of photoacoustic system are: center of resonant frequency of 833Hz, quality factor of 20.8, and photoacoustic cell of 2323Pacm/W. When laser power is 3.6W, photoacoustic signal and ethylene volume fraction get good linear relationship under the irradiation of two laser spectrum. Linear fit is 0.99744 and 0.99802 respectively. The minimum detectable concentration of system is 0.9nmol/L. Experimental results and theoretical analysis verify the effect of photoacoustic spectroscopy detection of trace concentrations of ethylene has good appliciation value.
2016, 40(3): 432-435.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.028
Abstract:
In order to improve the wear resistance of 45# steel, NiCoFeCrTi high entropy alloy coating was obtained by CO2 laser cladding on 45# steel. The phase structure, microstructure and chemical composition of NiCoFeCrTi high entropy alloy layer were analyzed by X-ray diffraction scanning electron microscope(SEM) and energy dispersive spectroscopy respectively. The result shows that the phase structure of NiCoFeCrTi high entropy alloy coating is face-centered cubic structure due to high-entropy effect. There are no micro-cracks in the cladding zone, the bounding zone and heat affected zone of NiCoFeCrTi high entropy alloy samples. The analysis of microstructure by SEM shows that the coating is metallurgically bonded to the substrate. The surface microhardness of NiCoFeCrTi high entropy alloys samples is up to 940HV, about 3 times that of the substrate. The wear volume loss of 45# steel sample with NiCoFeCrTi high entropy alloy coating is 5.010-10m3/m, less than 8.110-10m3/m of 45# steel. The results show that, NiCoFeCrTi high entropy alloy coating prepared by laser cladding technology can significantly improve the wear resistance of 45# steel and it is meaningful to coating applications.
In order to improve the wear resistance of 45# steel, NiCoFeCrTi high entropy alloy coating was obtained by CO2 laser cladding on 45# steel. The phase structure, microstructure and chemical composition of NiCoFeCrTi high entropy alloy layer were analyzed by X-ray diffraction scanning electron microscope(SEM) and energy dispersive spectroscopy respectively. The result shows that the phase structure of NiCoFeCrTi high entropy alloy coating is face-centered cubic structure due to high-entropy effect. There are no micro-cracks in the cladding zone, the bounding zone and heat affected zone of NiCoFeCrTi high entropy alloy samples. The analysis of microstructure by SEM shows that the coating is metallurgically bonded to the substrate. The surface microhardness of NiCoFeCrTi high entropy alloys samples is up to 940HV, about 3 times that of the substrate. The wear volume loss of 45# steel sample with NiCoFeCrTi high entropy alloy coating is 5.010-10m3/m, less than 8.110-10m3/m of 45# steel. The results show that, NiCoFeCrTi high entropy alloy coating prepared by laser cladding technology can significantly improve the wear resistance of 45# steel and it is meaningful to coating applications.
2016, 40(3): 436-440.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.029
Abstract:
In order to realize real-time position and posture measurement of kinetic objects with high precision, based on measurement principle of geographic coordinates with laser trackers, the fore and aft parts of a kinetic object were aimed at with two laser trackers respectively. Both the laser trackers were triggered to collect data synchronously, and real-time spatial coordinates of the fore and aft parts of the kinetic object were obtained. The position and posture of the kinetic object in spatial geographic coordinate were measured. The spatial position and posture were calculated with a software developed by ourselves. After theoretical analysis and experimental verification, the results show that the stability and precision of the measurement system are pretty well and the proposed method can satisfy the high precision requirements for measurement of spatial position and posture.
In order to realize real-time position and posture measurement of kinetic objects with high precision, based on measurement principle of geographic coordinates with laser trackers, the fore and aft parts of a kinetic object were aimed at with two laser trackers respectively. Both the laser trackers were triggered to collect data synchronously, and real-time spatial coordinates of the fore and aft parts of the kinetic object were obtained. The position and posture of the kinetic object in spatial geographic coordinate were measured. The spatial position and posture were calculated with a software developed by ourselves. After theoretical analysis and experimental verification, the results show that the stability and precision of the measurement system are pretty well and the proposed method can satisfy the high precision requirements for measurement of spatial position and posture.
2016, 40(3): 441-446.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.030
Abstract:
For eliminating the effects of weight and thermal stress on the surface accuracy of a large flat mirror, the surface accuracy was analyzed for the back fixed constraint and the back float constraint structures at -20℃ by means of the finite element method. The design of support structure using finite element method was studied. By using the back fixed constraint and the float constraint at -20℃, the simulation data of mirror surface accuracy was obtained and analyzed comparatively. The back suspension support structure for dynamic scanning mirrors was designed to achieve the back float constraint. After the establishment of detection platform, the profile of the large flat mirror was measured. The results show that the values of peak-to-valley and root mean square of the flat mirror with back suspension support structure were 0.236 and 0.049 respectively. The back suspension support structure could achieve float constraint and release the surface shape deformation of large flat mirrors caused by weight and thermal stress and ensure the surface accuracy effectively.
For eliminating the effects of weight and thermal stress on the surface accuracy of a large flat mirror, the surface accuracy was analyzed for the back fixed constraint and the back float constraint structures at -20℃ by means of the finite element method. The design of support structure using finite element method was studied. By using the back fixed constraint and the float constraint at -20℃, the simulation data of mirror surface accuracy was obtained and analyzed comparatively. The back suspension support structure for dynamic scanning mirrors was designed to achieve the back float constraint. After the establishment of detection platform, the profile of the large flat mirror was measured. The results show that the values of peak-to-valley and root mean square of the flat mirror with back suspension support structure were 0.236 and 0.049 respectively. The back suspension support structure could achieve float constraint and release the surface shape deformation of large flat mirrors caused by weight and thermal stress and ensure the surface accuracy effectively.
2016, 40(3): 447-450.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.031
Abstract:
The reliability and the usability of mechanical products largely depend on their surface roughness. In order to achieve long-distance measurement of surface roughness of mechanical parts, a method of electronic direct modulation laser coherence based on laser Doppler effects was put forward to measure the surface roughness. The application of laser Doppler effects can reduce influence of working distance. The speed of measurement was improved and the cost was reduced by using electronic direct modulation method. By using coherent method, alternative phase lock amplification was realized and the system noise was effectively controlled too. The experimental results show that the uncertainty degree of the measurement system can be reached 1 after controlling the statistical error and calibrating the experiment data during measurement process. The study has a certain guiding significance on the measurement of surface roughness.
The reliability and the usability of mechanical products largely depend on their surface roughness. In order to achieve long-distance measurement of surface roughness of mechanical parts, a method of electronic direct modulation laser coherence based on laser Doppler effects was put forward to measure the surface roughness. The application of laser Doppler effects can reduce influence of working distance. The speed of measurement was improved and the cost was reduced by using electronic direct modulation method. By using coherent method, alternative phase lock amplification was realized and the system noise was effectively controlled too. The experimental results show that the uncertainty degree of the measurement system can be reached 1 after controlling the statistical error and calibrating the experiment data during measurement process. The study has a certain guiding significance on the measurement of surface roughness.
2016, 40(3): 451-455.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.032
Abstract:
To make up for the deafness of ultraviolet directional communication, a multi-channel media access control protocol for airborne ultraviolet communication based on space division multiplexing was designed and an ultraviolet communication network model was established. Several UV transceivers with different directions were installed on an ultraviolet node to realize multi-channel information exchange. The performance of the new protocol was simulated and evaluated. The results show that compared with the single-channel communication protocol, the multi-channel communication protocol has the characteristics of low delay and high throughput so that the deafness problem can be significantly alleviated and the network performance is greatly improved. Three-channel communication mode is the best option.
To make up for the deafness of ultraviolet directional communication, a multi-channel media access control protocol for airborne ultraviolet communication based on space division multiplexing was designed and an ultraviolet communication network model was established. Several UV transceivers with different directions were installed on an ultraviolet node to realize multi-channel information exchange. The performance of the new protocol was simulated and evaluated. The results show that compared with the single-channel communication protocol, the multi-channel communication protocol has the characteristics of low delay and high throughput so that the deafness problem can be significantly alleviated and the network performance is greatly improved. Three-channel communication mode is the best option.
2016, 40(3): 456-460.
doi: 10.7510/jgjs.issn.1001-3806.2016.03.033
Abstract:
In order to study influence of atmospheric turbulence on the Rayleigh range of partially coherent cosh-Gaussian beams, analytical analysis and numerical simulation were carried out. It is found that the Rayleigh range increases with the increase of laser coherent beam intensity, Gaussian waist and the inner scale of atmospheric turbulence and decreases with the increase of atmospheric refractive index fluctuation intensity and laser wavelength. The results show that effect of the inner scale of atmospheric turbulence on the Rayleigh range is significant, but the influence of outer scale is weak. The Rayleigh range depends on air quality and laser properties.
In order to study influence of atmospheric turbulence on the Rayleigh range of partially coherent cosh-Gaussian beams, analytical analysis and numerical simulation were carried out. It is found that the Rayleigh range increases with the increase of laser coherent beam intensity, Gaussian waist and the inner scale of atmospheric turbulence and decreases with the increase of atmospheric refractive index fluctuation intensity and laser wavelength. The results show that effect of the inner scale of atmospheric turbulence on the Rayleigh range is significant, but the influence of outer scale is weak. The Rayleigh range depends on air quality and laser properties.
